image/spec: Add Go structs
- Related to: https://github.com/moby/moby/pull/46313

This is an initial effort to add a canonical implementation of the Docker Image spec (`application/vnd.docker.container.image.v1+json`).

The intent was to share as much of the implementation with the [OCI image spec](https://github.com/opencontainers/image-spec) and allow for easy conversion between OCI image and Docker OCI image.


**- What I did**
Add Go structs describing the image spec which extend the OCI types.

**- How I did it**

**- How to verify it**

**- Description for the changelog**
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api/types/container/config.go
package container // import "github.com/docker/docker/api/types/container"

import (
	"io"
	"time"

	"github.com/docker/docker/api/types/strslice"
	"github.com/docker/go-connections/nat"
)

// MinimumDuration puts a minimum on user configured duration.
// This is to prevent API error on time unit. For example, API may
// set 3 as healthcheck interval with intention of 3 seconds, but
// Docker interprets it as 3 nanoseconds.
const MinimumDuration = 1 * time.Millisecond

// StopOptions holds the options to stop or restart a container.
type StopOptions struct {
	// Signal (optional) is the signal to send to the container to (gracefully)
	// stop it before forcibly terminating the container with SIGKILL after the
	// timeout expires. If not value is set, the default (SIGTERM) is used.
	Signal string `json:",omitempty"`

	// Timeout (optional) is the timeout (in seconds) to wait for the container
	// to stop gracefully before forcibly terminating it with SIGKILL.
	//
	// - Use nil to use the default timeout (10 seconds).
	// - Use '-1' to wait indefinitely.
	// - Use '0' to not wait for the container to exit gracefully, and
	//   immediately proceeds to forcibly terminating the container.
	// - Other positive values are used as timeout (in seconds).
	Timeout *int `json:",omitempty"`
}

// HealthConfig holds configuration settings for the HEALTHCHECK feature.
type HealthConfig struct {
	// Test is the test to perform to check that the container is healthy.
	// An empty slice means to inherit the default.
	// The options are:
	// {} : inherit healthcheck
	// {"NONE"} : disable healthcheck
	// {"CMD", args...} : exec arguments directly
	// {"CMD-SHELL", command} : run command with system's default shell
	Test []string `json:",omitempty"`

	// Zero means to inherit. Durations are expressed as integer nanoseconds.
	Interval      time.Duration `json:",omitempty"` // Interval is the time to wait between checks.
	Timeout       time.Duration `json:",omitempty"` // Timeout is the time to wait before considering the check to have hung.
	StartPeriod   time.Duration `json:",omitempty"` // The start period for the container to initialize before the retries starts to count down.
	StartInterval time.Duration `json:",omitempty"` // The interval to attempt healthchecks at during the start period

	// Retries is the number of consecutive failures needed to consider a container as unhealthy.
	// Zero means inherit.
	Retries int `json:",omitempty"`
}

// ExecStartOptions holds the options to start container's exec.
type ExecStartOptions struct {
	Stdin       io.Reader
	Stdout      io.Writer
	Stderr      io.Writer
	ConsoleSize *[2]uint `json:",omitempty"`
}

// Config contains the configuration data about a container.
// It should hold only portable information about the container.
// Here, "portable" means "independent from the host we are running on".
// Non-portable information *should* appear in HostConfig.
// All fields added to this struct must be marked `omitempty` to keep getting
// predictable hashes from the old `v1Compatibility` configuration.
type Config struct {
	Hostname        string              // Hostname
	Domainname      string              // Domainname
	User            string              // User that will run the command(s) inside the container, also support user:group
	AttachStdin     bool                // Attach the standard input, makes possible user interaction
	AttachStdout    bool                // Attach the standard output
	AttachStderr    bool                // Attach the standard error
	ExposedPorts    nat.PortSet         `json:",omitempty"` // List of exposed ports
	Tty             bool                // Attach standard streams to a tty, including stdin if it is not closed.
	OpenStdin       bool                // Open stdin
	StdinOnce       bool                // If true, close stdin after the 1 attached client disconnects.
	Env             []string            // List of environment variable to set in the container
	Cmd             strslice.StrSlice   // Command to run when starting the container
	Healthcheck     *HealthConfig       `json:",omitempty"` // Healthcheck describes how to check the container is healthy
	ArgsEscaped     bool                `json:",omitempty"` // True if command is already escaped (meaning treat as a command line) (Windows specific).
	Image           string              // Name of the image as it was passed by the operator (e.g. could be symbolic)
	Volumes         map[string]struct{} // List of volumes (mounts) used for the container
	WorkingDir      string              // Current directory (PWD) in the command will be launched
	Entrypoint      strslice.StrSlice   // Entrypoint to run when starting the container
	NetworkDisabled bool                `json:",omitempty"` // Is network disabled
	MacAddress      string              `json:",omitempty"` // Mac Address of the container
	OnBuild         []string            // ONBUILD metadata that were defined on the image Dockerfile
	Labels          map[string]string   // List of labels set to this container
	StopSignal      string              `json:",omitempty"` // Signal to stop a container
	StopTimeout     *int                `json:",omitempty"` // Timeout (in seconds) to stop a container
	Shell           strslice.StrSlice   `json:",omitempty"` // Shell for shell-form of RUN, CMD, ENTRYPOINT
}

package container // import "github.com/docker/docker/api/types/container"

import (
	"io"
	"time"

	"github.com/docker/docker/api/types/strslice"
	dockerspec "github.com/docker/docker/image/spec/specs-go/v1"
	"github.com/docker/go-connections/nat"
)

// MinimumDuration puts a minimum on user configured duration.
// This is to prevent API error on time unit. For example, API may
// set 3 as healthcheck interval with intention of 3 seconds, but
// Docker interprets it as 3 nanoseconds.
const MinimumDuration = 1 * time.Millisecond

// StopOptions holds the options to stop or restart a container.
type StopOptions struct {
	// Signal (optional) is the signal to send to the container to (gracefully)
	// stop it before forcibly terminating the container with SIGKILL after the
	// timeout expires. If not value is set, the default (SIGTERM) is used.
	Signal string `json:",omitempty"`

	// Timeout (optional) is the timeout (in seconds) to wait for the container
	// to stop gracefully before forcibly terminating it with SIGKILL.
	//
	// - Use nil to use the default timeout (10 seconds).
	// - Use '-1' to wait indefinitely.
	// - Use '0' to not wait for the container to exit gracefully, and
	//   immediately proceeds to forcibly terminating the container.
	// - Other positive values are used as timeout (in seconds).
	Timeout *int `json:",omitempty"`
}

// HealthConfig holds configuration settings for the HEALTHCHECK feature.
type HealthConfig = dockerspec.HealthcheckConfig

// ExecStartOptions holds the options to start container's exec.
type ExecStartOptions struct {
	Stdin       io.Reader
	Stdout      io.Writer
	Stderr      io.Writer
	ConsoleSize *[2]uint `json:",omitempty"`
}

// Config contains the configuration data about a container.
// It should hold only portable information about the container.
// Here, "portable" means "independent from the host we are running on".
// Non-portable information *should* appear in HostConfig.
// All fields added to this struct must be marked `omitempty` to keep getting
// predictable hashes from the old `v1Compatibility` configuration.
type Config struct {
	Hostname        string              // Hostname
	Domainname      string              // Domainname
	User            string              // User that will run the command(s) inside the container, also support user:group
	AttachStdin     bool                // Attach the standard input, makes possible user interaction
	AttachStdout    bool                // Attach the standard output
	AttachStderr    bool                // Attach the standard error
	ExposedPorts    nat.PortSet         `json:",omitempty"` // List of exposed ports
	Tty             bool                // Attach standard streams to a tty, including stdin if it is not closed.
	OpenStdin       bool                // Open stdin
	StdinOnce       bool                // If true, close stdin after the 1 attached client disconnects.
	Env             []string            // List of environment variable to set in the container
	Cmd             strslice.StrSlice   // Command to run when starting the container
	Healthcheck     *HealthConfig       `json:",omitempty"` // Healthcheck describes how to check the container is healthy
	ArgsEscaped     bool                `json:",omitempty"` // True if command is already escaped (meaning treat as a command line) (Windows specific).
	Image           string              // Name of the image as it was passed by the operator (e.g. could be symbolic)
	Volumes         map[string]struct{} // List of volumes (mounts) used for the container
	WorkingDir      string              // Current directory (PWD) in the command will be launched
	Entrypoint      strslice.StrSlice   // Entrypoint to run when starting the container
	NetworkDisabled bool                `json:",omitempty"` // Is network disabled
	MacAddress      string              `json:",omitempty"` // Mac Address of the container
	OnBuild         []string            // ONBUILD metadata that were defined on the image Dockerfile
	Labels          map[string]string   // List of labels set to this container
	StopSignal      string              `json:",omitempty"` // Signal to stop a container
	StopTimeout     *int                `json:",omitempty"` // Timeout (in seconds) to stop a container
	Shell           strslice.StrSlice   `json:",omitempty"` // Shell for shell-form of RUN, CMD, ENTRYPOINT
}

(not 100% sure if we need to add the "is an alias for", as some of that could potentially change in future if the OCI would accept it to be added to the spec).