feat(replace-participant): Add replaceParticipant feature-flag

conference.js

     p2pStatusChanged,
     sendLocalParticipant
 } from './react/features/base/conference';
+import { getReplaceParticipant } from './react/features/base/config/functions';
 import {
     checkAndNotifyForNewDevice,
     getAvailableDevices,
 
         // not enough rights to create conference
         case JitsiConferenceErrors.AUTHENTICATION_REQUIRED: {
-            const { replaceParticipant }
-                = APP.store.getState()['features/base/config'];
 
+            const replaceParticipant = getReplaceParticipant(APP.store.getState());
 
             // Schedule reconnect to check if someone else created the room.
             this.reconnectTimeout = setTimeout(() => {
      *
      */
     connect() {
-        const { replaceParticipant } = APP.store.getState()['features/base/config'];
+        const replaceParticipant = getReplaceParticipant(APP.store.getState());
 
         // the local storage overrides here and in connection.js can be used by jibri
         room.join(jitsiLocalStorage.getItem('xmpp_conference_password_override'), replaceParticipant);

modules/UI/authentication/AuthHandler.js

     isTokenAuthEnabled,
     getTokenAuthUrl
 } from '../../../react/features/authentication/functions';
+import { getReplaceParticipant } from '../../../react/features/base/config/functions';
 import { isDialogOpen } from '../../../react/features/base/dialog';
 import { setJWT } from '../../../react/features/base/jwt';
 import UIUtil from '../util/UIUtil';
     }).then(url => {
         // de-authenticate conference on the fly
         if (room.isJoined()) {
-            const { replaceParticipant }
-                = APP.store.getState()['features/base/config'];
+            const replaceParticipant = getReplaceParticipant(APP.store.getState());
 
             room.join(null, replaceParticipant);
         }

react/features/base/conference/actions.js

 } from '../../analytics';
 import { getName } from '../../app/functions';
 import { endpointMessageReceived } from '../../subtitles';
+import { getReplaceParticipant } from '../config/functions';
 import { JITSI_CONNECTION_CONFERENCE_KEY } from '../connection';
 import { JitsiConferenceEvents } from '../lib-jitsi-meet';
 import { MEDIA_TYPE, setAudioMuted, setVideoMuted } from '../media';
 
         sendLocalParticipant(state, conference);
 
-        conference.join(password, config.replaceParticipant);
+        const replaceParticipant = getReplaceParticipant(state);
+
+        conference.join(password, replaceParticipant);
     };
 }
 
         const { authRequired, password }
             = getState()['features/base/conference'];
 
-        const { replaceParticipant }
-            = getState()['features/base/config'];
+        const replaceParticipant = getReplaceParticipant(APP.store.getState());
 
         authRequired && dispatch(_conferenceWillJoin(authRequired));
         authRequired && authRequired.join(password, replaceParticipant);

react/features/base/config/functions.native.js

 
 import { NativeModules } from 'react-native';
 
+import { getFeatureFlag, REPLACE_PARTICIPANT } from '../flags';
+
 export * from './functions.any';
 
 /**
         delete config.callStatsSecret;
     }
 }
+
+/**
+ * Returns the replaceParticipant config.
+ *
+ * @param {Object} state - The state of the app.
+ * @returns {boolean}
+ */
+export function getReplaceParticipant(state: Object): string {
+    return getFeatureFlag(state, REPLACE_PARTICIPANT, false);
+}

react/features/base/config/functions.web.js

     return state['features/base/config'].guestDialOutUrl;
 }
 
+/**
+ * Returns the replaceParticipant config.
+ *
+ * @param {Object} state - The state of the app.
+ * @returns {boolean}
+ */
+export function getReplaceParticipant(state: Object): string {
+    return state['features/base/config'].replaceParticipant;
+}
+
 /**
  * Returns the list of enabled toolbar buttons.
  *

react/features/base/flags/constants.js

  */
 export const RECORDING_ENABLED = 'recording.enabled';
 
+/**
+ * Flag indicating if the user should join the conference with the replaceParticipant functionality.
+ * Default: (false).
+ */
+export const REPLACE_PARTICIPANT = 'replace.participant';
+
 /**
  * Flag indicating the local and (maximum) remote video resolution. Overrides
  * the server configuration.