Merge pull request #944 from redboltz/add_clear_user_pass

Added clear username and password functionality.

Author: redboltz

include/mqtt/client.hpp

@@ -921,6 +921,17 @@ class client : public endpoint<std::mutex, std::lock_guard, PacketIdBytes> {
         user_name_ = force_move(name);
     }
 
+    /**
+     * @brief Clear username.
+     *
+     * This function should be called before calling connect().<BR>
+     * See https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901071<BR>
+     * 3.1.3.5 User Name
+     */
+    void set_user_name() {
+        user_name_ = nullopt;
+    }
+
     /**
      * @brief Set password.
      * @param password password
@@ -933,6 +944,17 @@ class client : public endpoint<std::mutex, std::lock_guard, PacketIdBytes> {
         password_ = force_move(password);
     }
 
+    /**
+     * @brief Clear password.
+     *
+     * This function should be called before calling connect().<BR>
+     * See https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901072<BR>
+     * 3.1.3.6 Password
+     */
+    void set_password() {
+        password_ = nullopt;
+    }
+
     /**
      * @brief Set will.
      * @param w will