Add managed hybrid call widgets when supported

If your homeserver is configured with an experiment `widget_build_url`, this
will take over the functionality of the call buttons and turn them into a
general widget installer.

src/utils/WidgetUtils.ts

@@ -27,7 +27,7 @@ import {Room} from "matrix-js-sdk/src/models/room";
 import {WidgetType} from "../widgets/WidgetType";
 import {objectClone} from "./objects";
 import {_t} from "../languageHandler";
-import {Capability, IWidgetData, MatrixCapabilities} from "matrix-widget-api";
+import {Capability, IWidget, IWidgetData, MatrixCapabilities} from "matrix-widget-api";
 import {IApp} from "../stores/WidgetStore";
 
 // How long we wait for the state event echo to come back from the server
@@ -297,6 +297,16 @@ export default class WidgetUtils {
             content = {};
         }
 
+        return WidgetUtils.setRoomWidgetContent(roomId, widgetId, content);
+    }
+
+    static setRoomWidgetContent(
+        roomId: string,
+        widgetId: string,
+        content: IWidget,
+    ) {
+        const addingWidget = !!content.url;
+
         WidgetEchoStore.setRoomWidgetEcho(roomId, widgetId, content);
 
         const client = MatrixClientPeg.get();