daemon: Add access control headers to the search endpoint.

These headers are important for riot to be able to use pan's search
endpoint instead of the default Homeserver endpoint. It fails to search
using pan with CORS errors.

pantalaimon/daemon.py

@@ -905,6 +905,17 @@ class ProxyDaemon:
             data=json.dumps(sanitized_content)
         )
 
+    async def search_opts(self, request):
+        headers = {
+            "Access-Control-Allow-Headers": (
+                "Origin, X-Requested-With, Content-Type, Accept, Authorization"
+            ),
+            "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
+            "Access-Control-Allow-Origin": "*",
+        }
+
+        return web.json_response({}, headers=headers)
+
     async def search(self, request):
         access_token = self.get_access_token(request)
 
@@ -942,7 +953,11 @@ class ProxyDaemon:
         except UnknownRoomError:
             return await self.forward_to_web(request)
 
-        return web.json_response(result, status=200)
+        return web.json_response(
+            result,
+            headers={"Access-Control-Allow-Origin": "*"},
+            status=200
+        )
 
     async def shutdown(self, _):
         """Shut the daemon down closing all the client sessions it has.

pantalaimon/main.py

@@ -68,6 +68,7 @@ async def init(data_dir, server_conf, send_queue, recv_queue):
         ),
         web.post("/_matrix/client/r0/user/{user_id}/filter", proxy.filter),
         web.post("/_matrix/client/r0/search", proxy.search),
+        web.options("/_matrix/client/r0/search", proxy.search_opts),
     ])
     app.router.add_route("*", "/" + "{proxyPath:.*}", proxy.router)
     app.on_shutdown.append(proxy.shutdown)