Show typed error when matrix_2_0 mode is forced without homeserver MSC4354 support (#4017)

Show typed error when matrix_2_0 mode is forced without homeserver MSC4354 support

src/utils/errors.ts

@@ -21,6 +21,7 @@ export enum ErrorCode {
   /** LiveKit indicates that the server has hit its track limits */
   INSUFFICIENT_CAPACITY_ERROR = "INSUFFICIENT_CAPACITY_ERROR",
   E2EE_NOT_SUPPORTED = "E2EE_NOT_SUPPORTED",
+  STICKY_EVENTS_NOT_SUPPORTED = "STICKY_EVENTS_NOT_SUPPORTED",
   OPEN_ID_ERROR = "OPEN_ID_ERROR",
   NO_MATRIX_2_AUTHORIZATION_SERVICE = "NO_MATRIX_2_0_AUTHORIZATION_SERVICE",
   SFU_ERROR = "SFU_ERROR",
@@ -125,6 +126,22 @@ export class MembershipManagerError extends ElementCallError {
   }
 }
 
+/**
+ * Error indicating that this deployment pins `matrix_rtc_mode=matrix_2_0` in
+ * config.json but the homeserver does not advertise MSC4354 (sticky events),
+ * which the Matrix 2.0 mode requires.
+ */
+export class StickyEventsRequiredError extends ElementCallError {
+  public constructor() {
+    super(
+      t("error.sticky_events_required"),
+      ErrorCode.STICKY_EVENTS_NOT_SUPPORTED,
+      ErrorCategory.CONFIGURATION_ISSUE,
+      t("error.sticky_events_required_description"),
+    );
+  }
+}
+
 /**
  * Error indicating that end-to-end encryption is not supported in the current environment.
  */