Add ability to set initial user status.

Setting the status after joining (using the "setstatus" action)
may cause multiple "user" messages to be sent to clients.  Add
the ability to set the initial status at join time.

README.PROTOCOL

@@ -107,7 +107,8 @@ The `join` message requests that the sender join or leave a group:
     kind: 'join' or 'leave',
     group: group,
     username: username,
-    password: password
+    password: password,
+    status: status
 }
 ```
 

rtpconn/webclient.go

@@ -1316,9 +1316,20 @@ func handleClientMessage(c *webClient, m clientMessage) error {
 		}
 
 		if c.group != nil {
-			return group.ProtocolError("cannot join multiple groups")
+			return group.ProtocolError(
+				"cannot join multiple groups",
+			)
 		}
 		c.username = m.Username
+		if m.Status != nil {
+			s, ok := m.Status.(map[string]interface{})
+			if !ok {
+				return group.ProtocolError(
+					"bad type for status",
+				)
+			}
+			c.status = s
+		}
 		g, err := group.AddClient(m.Group, c,
 			group.ClientCredentials{
 				Username: m.Username,

static/protocol.js

@@ -416,15 +416,19 @@ ServerConnection.prototype.connect = async function(url) {
  * @param {string} group - The name of the group to join.
  * @param {string} username - the username to join as.
  * @param {string} password - the password.
+ * @param {Object<string,any>} [status] - the initial status of the user.
  */
-ServerConnection.prototype.join = function(group, username, password) {
-    this.send({
+ServerConnection.prototype.join = function(group, username, password, status) {
+    let m = {
         type: 'join',
         kind: 'join',
         group: group,
         username: username,
         password: password,
-    });
+    };
+    if(status)
+        m.status = status;
+    this.send(m);
 };
 
 /**