Send a 'join' action when entering the call

Following a75952cf77, this is one more upgrade to the widget communication that I'd like to make within this release cycle.

The motivating issue is https://github.com/element-hq/element-web/issues/29429. Fundamentally, without a 'join' action, the only info Element Web can use to determine whether it's joined the call is whether a MatrixRTC membership exists. But membership state events can inaccurately represent the client's actual state (whether because delayed events aren't supported, or because the delayed event hasn't timed out yet), so I suggest we send a 'join' action here just as we do in the Element Web Jitsi wrapper (e9a3625bd6/src/vector/jitsi/index.ts (L503)) to let Element Web tap directly into the widget's local state. (This will need additional Element Web changes, but is certainly backwards compatible.)

src/rtcSessionHelpers.ts

@@ -116,6 +116,13 @@ export async function enterRTCSession(
       makeKeyDelay: matrixRtcSessionConfig?.key_rotation_on_leave_delay,
     },
   );
+  if (widget) {
+    try {
+      await widget.api.transport.send(ElementWidgetActions.JoinCall, {});
+    } catch (e) {
+      logger.error("Failed to send join action", e);
+    }
+  }
 }
 
 const widgetPostHangupProcedure = async (
@@ -135,7 +142,20 @@ const widgetPostHangupProcedure = async (
   // We send the hangup event after the memberships have been updated
   // calling leaveRTCSession.
   // We need to wait because this makes the client hosting this widget killing the IFrame.
-  await widget.api.transport.send(ElementWidgetActions.HangupCall, {});
+  try {
+    await widget.api.transport.send(ElementWidgetActions.HangupCall, {});
+  } catch (e) {
+    logger.error("Failed to send hangup action", e);
+  }
+  // To make the hangup procedure behave more similarly to what future versions
+  // of Element Call will do, we additionally send a close action (even though
+  // we're not yet employing the distinction between 'hangup' and 'close' to
+  // display error screens)
+  try {
+    await widget.api.transport.send(ElementWidgetActions.Close, {});
+  } catch (e) {
+    logger.error("Failed to send close action", e);
+  }
 };
 
 export async function leaveRTCSession(

src/widget.ts

@@ -17,10 +17,11 @@ import { getUrlParams } from "./UrlParams";
 import { Config } from "./config/Config";
 import { ElementCallReactionEventType } from "./reactions";
 
-// Subset of the actions in matrix-react-sdk
+// Subset of the actions in element-web
 export enum ElementWidgetActions {
   JoinCall = "io.element.join",
   HangupCall = "im.vector.hangup",
+  Close = "io.element.close",
   TileLayout = "io.element.tile_layout",
   SpotlightLayout = "io.element.spotlight_layout",
   // This can be sent as from or to widget