Feature: Moderator can revoke moderator role to others and himself (#1532)

* Feature: Moderator can revoke moderator role to others and himself

* Code review inputs

* Code review inputs

JitsiConference.js

@@ -1470,6 +1470,24 @@ JitsiConference.prototype.grantOwner = function(id) {
     this.room.setAffiliation(participant.getJid(), 'owner');
 };
 
+/**
+ * Revoke owner rights to the participant or local Participant as
+ * the user might want to refuse to be a moderator.
+ * @param {string} id id of the participant to revoke owner rights to.
+ */
+JitsiConference.prototype.revokeOwner = function(id) {
+    const participant = this.getParticipantById(id);
+    const isMyself = this.myUserId() === id;
+    const role = this.isMembersOnly() ? 'member' : 'none';
+
+    if (isMyself) {
+        this.room.setAffiliation(this.room.myroomjid, role);
+    } else if (participant) {
+        this.room.setAffiliation(participant.getJid(), role);
+    }
+};
+
+
 /**
  * Kick participant from this conference.
  * @param {string} id id of the participant to kick