Check Status Code of responses (especially for POST/PUT/DELETE requests)

[Art4]

After requesting the Redmine server in Redmine\Api\... classes we should check for the correct status code in the responses, see #341. Otherwise we should throw an UnexpectedResponseException, see #364.

Throwing an exception would be a breaking change, so this change has to be made in a forward compatible way, or in the next major version.

A FC way could look like this:

// in \Redmine\Api\Project
    public function update($id, array $params)
    {
        // ...

        $result = $this->put(
            '/projects/' . $id . '.xml',
            XmlSerializer::createFromArray(['project' => $params])->getEncoded()
        );

        $lastResponse = $this->getLastResponse();

        if ($lastResponse->getStatusCode() !== 204) {
            if (!defined('PHP_REDMINE_API_THROW_EXCEPTIONS_ON_STATUS_CODE_MISSMATCH') || PHP_REDMINE_API_THROW_EXCEPTIONS_ON_STATUS_CODE_MISSMATCH !== true) {
                trigger_error(
                    sprintf(
                        'The Redmine server replied with the status code %d in %s(), starting with v2.0.0 this will throw an %s. Define the constant `%s` to throw the exceptions now.',
                        $lastResponse->getStatusCode(),
                        __METHOD__,
                        UnexpectedResponseException::class,
                        'PHP_REDMINE_API_THROW_EXCEPTIONS_ON_STATUS_CODE_MISSMATCH'
                    ),
                    E_USER_DEPRECATED
                );

                return $result;
            }

            throw new UnexpectedResponseException($lastResponse);
        }

        return true;
    }

In v3 we could just remove the check.

// in \Redmine\Api\Project
    public function update($id, array $params)
    {
        // ...

        $result = $this->put(
            '/projects/' . $id . '.xml',
            XmlSerializer::createFromArray(['project' => $params])->getEncoded()
        );

        $lastResponse = $this->getLastResponse();

        if ($lastResponse->getStatusCode() !== 204) {
            throw new UnexpectedResponseException($lastResponse);
        }

        return true;
    }