Prototyped several interfaces, added basic topics stuff and exception.

src/ClientInterface.php

@@ -8,13 +8,39 @@ interface ClientInterface {
    * Login using credentials.
    *
    * @param string $login
-   *
+   *   User login.
    * @param string $password
+   *   User password.
    *
-   * @throws InvalidAuthCredentials
-   *
-   * @return void
+   * @throws \Toloka\PhpApi\Exception\Auth\InvalidAuthCredentials
+   * @throws \Toloka\PhpApi\Exception\Auth\TooManyLoginAttempts
+   * @throws \Psr\Http\Client\ClientExceptionInterface
    */
   public function login(string $login, string $password): void;
 
+  /**
+   * Check if user logged in.
+   *
+   * @return bool
+   */
+  public function isLoggedIn(): bool;
+
+  /**
+   * Perform user's logout.
+   *
+   * @throws \Psr\Http\Client\ClientExceptionInterface
+   */
+  public function logout(): void;
+
+  /**
+   * Get topic by ID.
+   *
+   * @param int $id
+   *   Integer serial number of topic.
+   *
+   * @return TopicInterface
+   *   Object with populated topic data.
+   */
+  public function getTopic(int $id): TopicInterface;
+
 }