src/Eloquent/Concerns/SoftDeletesModels.php
protected function getSoftDeleteField(Model $record)
    {
        if ($field = $this->softDeleteField()) {
            return $field;
        }

        $key = $this->getSoftDeleteKey($record);

        return Str::dasherize($key);
    }
protected function getSoftDeleteField(Model $record)
    {
        if ($field = $this->softDeleteField()) {
            return $field;
        }

        $key = $this->getSoftDeleteKey($record);

        return Str::dasherize($key);
    }
Get the JSON API field that is used for the soft-delete value.

@param Model $record
@return string