src/XQueue/Maileon/API/Contacts/ContactsService.php
function renameCustomField($oldName, $newName)
    {
        $encodedOldName = urlencode(mb_convert_encoding($oldName, "UTF-8"));
        $encodedNewName = urlencode(mb_convert_encoding($newName, "UTF-8"));
        return $this->put("contacts/fields/custom/${encodedOldName}/${encodedNewName}");
    }
function renameCustomField($oldName, $newName)
    {
        $encodedOldName = urlencode(mb_convert_encoding($oldName, "UTF-8"));
        $encodedNewName = urlencode(mb_convert_encoding($newName, "UTF-8"));
        return $this->put("contacts/fields/custom/${encodedOldName}/${encodedNewName}");
    }
Renames a custom contact field. The data type and the recorded values for
the contacts remain unchanged.

@param string $oldName
the current name of the field
@param string $newName
the new name of the field
@return \em com_maileon_api_MaileonAPIResult
the result object of the API call
@throws com_maileon_api_MaileonAPIException
if there was a connection problem or a server error occurred