mark HttpClient, Request and Response as internal

Author: Art4

src/Redmine/Http/HttpClient.php

@@ -14,6 +14,8 @@
  *
  * The client is responsible for ensuring that all data is sent in the correct form and
  * that received data is processed correctly.
+ *
+ * @internal
  */
 interface HttpClient
 {

src/Redmine/Http/Request.php

@@ -9,6 +9,8 @@
  *
  * The method signatures are defined with the intention that an implementing class
  * can implment this interface and also the PSR-7 `\Psr\Http\Message\RequestInterface`
+ *
+ * @internal
  */
 interface Request
 {

src/Redmine/Http/Response.php

@@ -9,6 +9,8 @@
  *
  * The method signatures are defined with the intention that an implementing class
  * can implment this interface and also the PSR-7 `\Psr\Http\Message\ResponseInterface`
+ *
+ * @internal
  */
 interface Response
 {