fix(bbb-html5): customHeartbeat would not close stale sessions, + (bi…

…gbluebutton#19017)

* fix(bbb-html5): customHeartbeat would not close stale sessions, +

The [disabled by default] custom heartbeat included in Meteor's server
does not end connections when they are considered unhealthy/stale, which
deviates a bit from the default implementation. See:
bigbluebutton#11486.

This commit includes a call to the default heartbeat termination timeout
so sockets are correctly cleaned up when the custom heartbeat is
activated. It also adds a customHeartbeatUseDataFrames config to allow
controlling whether the custom heartbeat should use WS data frames as
valid heartbeats as well - this should only be useful for
testing/debugging purposes and the default behavior (true) is
maintained.

As a side note: this change spun off from an investigation where some
problematic networks were triggering periodic client re-connects due to
the default heartbeat failing. Investigation points to the control
frames being put alongside fragmented WS data frames and the server side
failing to recognize the former - which means pong frames would be missed and
the health check would fail. Since the default heartbeat _does not_
account for data frame traffic (eg DDP payloads), it would shut down the
client's WS even though it was healthy.
The custom heartbeat _does_ account for data frames, which mitigates
that scenario and prevents unecessary reconnections.

* fix(bbb-html5): frontend crash due to undefined vars in customHeartbeat

Meteor frontends may crash when customHeartbeat is enabled
due to an undefined access in the heartbeat`s logger.

Add optional chaining to the session props access so it won`t crash and tune down some log levels around that area.

bigbluebutton-html5/imports/startup/server/index.js

@@ -83,10 +83,10 @@ Meteor.startup(() => {
           // Skipping heartbeat, because websocket is sending data
           if (currentTime - this.ws.lastSentFrameTimestamp < 10000) {
             try {
-              Logger.info('Skipping heartbeat, because websocket is sending data', {
+              Logger.debug('Skipping heartbeat, because websocket is sending data', {
                 currentTime,
                 lastSentFrameTimestamp: this.ws.lastSentFrameTimestamp,
-                userId: this.session.connection._meteorSession.userId,
+                userId: this.session?.connection?._meteorSession?.userId,
               });
               return;
             } catch (err) {
@@ -102,7 +102,7 @@ Meteor.startup(() => {
         if (supportsHeartbeats) {
           this.hto_ref = setTimeout(() => {
             try {
-              Logger.info('Heartbeat timeout', { userId: this.session.connection._meteorSession.userId, sentAt: currentTime, now: new Date().getTime() });
+              Logger.warn('Heartbeat timeout', { userId: this.session?.connection?._meteorSession?.userId, sentAt: currentTime, now: new Date().getTime() });
             } catch (err) {
               Logger.error(`Heartbeat timeout error: ${err}`);
             } finally {