fix(transport): remove legacy code

It has been around bor > 2.5 years already.

modules/transport/PostMessageTransportBackend.js

     window: window.opener || window.parent
 };
 
-/**
- * The list of methods of incoming postis messages that we have to support for
- * backward compatibility for the users that are directly sending messages to
- * Jitsi Meet (without using external_api.js)
- *
- * @type {string[]}
- */
-const LEGACY_INCOMING_METHODS = [
-    'avatar-url',
-    'display-name',
-    'email',
-    'toggle-audio',
-    'toggle-chat',
-    'toggle-film-strip',
-    'toggle-share-screen',
-    'toggle-video',
-    'video-hangup'
-];
-
-/**
- * The list of methods of outgoing postis messages that we have to support for
- * backward compatibility for the users that are directly listening to the
- * postis messages send by Jitsi Meet(without using external_api.js).
- *
- * @type {string[]}
- */
-const LEGACY_OUTGOING_METHODS = [
-    'display-name-change',
-    'incoming-message',
-    'outgoing-message',
-    'participant-joined',
-    'participant-left',
-    'video-conference-joined',
-    'video-conference-left',
-    'video-ready-to-close'
-];
-
 /**
  * The postis method used for all messages.
  *
      * @param {Object} options - Optional parameters for configuration of the
      * transport.
      */
-    constructor({ enableLegacyFormat, postisOptions } = {}) {
+    constructor({ postisOptions } = {}) {
         // eslint-disable-next-line new-cap
         this.postis = Postis({
             ...DEFAULT_POSTIS_OPTIONS,
             ...postisOptions
         });
 
-        /**
-         * If true PostMessageTransportBackend will process and send messages
-         * using the legacy format and in the same time the current format.
-         * Otherwise all messages (outgoing and incoming) that are using the
-         * legacy format will be ignored.
-         *
-         * @type {boolean}
-         */
-        this._enableLegacyFormat = enableLegacyFormat;
-
-        if (this._enableLegacyFormat) {
-            // backward compatibility
-            LEGACY_INCOMING_METHODS.forEach(method =>
-                this.postis.listen(
-                    method,
-                    params =>
-                        this._legacyMessageReceivedCallback(method, params)
-                )
-            );
-        }
-
         this._receiveCallback = () => {
             // Do nothing until a callback is set by the consumer of
             // PostMessageTransportBackend via setReceiveCallback.
             message => this._receiveCallback(message));
     }
 
-    /**
-     * Handles incoming legacy postis messages.
-     *
-     * @param {string} method - The method property from the postis message.
-     * @param {Any} params - The params property from the postis message.
-     * @returns {void}
-     */
-    _legacyMessageReceivedCallback(method, params = {}) {
-        this._receiveCallback({
-            data: {
-                name: method,
-                data: params
-            }
-        });
-    }
-
-    /**
-     * Sends the passed message via postis using the old format.
-     *
-     * @param {Object} legacyMessage - The message to be sent.
-     * @returns {void}
-     */
-    _sendLegacyMessage({ name, ...data }) {
-        if (name && LEGACY_OUTGOING_METHODS.indexOf(name) !== -1) {
-            this.postis.send({
-                method: name,
-                params: data
-            });
-        }
-    }
-
     /**
      * Disposes the allocated resources.
      *
             method: POSTIS_METHOD_NAME,
             params: message
         });
-
-        if (this._enableLegacyFormat) {
-            // For the legacy use case we don't need any new fields defined in
-            // Transport class. That's why we are passing only the original
-            // object passed by the consumer of the Transport class which is
-            // message.data.
-            this._sendLegacyMessage(message.data || {});
-        }
     }
 
     /**

modules/transport/index.js

  */
 export function getJitsiMeetTransport() {
     if (!transport) {
-        transport = new Transport({
-            backend: new PostMessageTransportBackend({
-                enableLegacyFormat: true,
-                postisOptions
-            })
-        });
+        transport = new Transport({ backend: new PostMessageTransportBackend({ postisOptions }) });
     }
 
     return transport;