test(messaging): sendFCM function that reflects a TokenMessage

- requires a TokenMessage, and just sends the Message to the device
  addressed by the token in the message
- optionally can have a delay so you can put a test app in background
  or kill it or similar after calling the API

For security purposes:
- Tested this with an incorrect google-services.json / plist and the function
  call simply fails
- Tested this with an incorrect package name and the function all also simply fails
- Tested it with a correct package name and you can send on android, but on iOS there
  is still a lot of Apple developer account / app work to do, so that fails.

.github/workflows/scripts/functions/src/index.ts

@@ -23,3 +23,4 @@ export { testFunctionCustomRegion } from './testFunctionCustomRegion';
 export { testFunctionDefaultRegionV2 } from './testFunctionDefaultRegion';
 export { testFunctionRemoteConfigUpdateV2 } from './testFunctionRemoteConfigUpdate';
 export { fetchAppCheckTokenV2 } from './fetchAppCheckToken';
+export { sendFCM } from './sendFCM';

.github/workflows/scripts/functions/src/sendFCM.ts

@@ -0,0 +1,28 @@
+/*
+ *
+ *  Testing tools for invertase/react-native-firebase use only.
+ *
+ *  Copyright (C) 2018-present Invertase Limited <oss@invertase.io>
+ *
+ *  See License file for more information.
+ */
+
+import * as functions from 'firebase-functions/v2';
+import { CallableRequest } from 'firebase-functions/v2/https';
+
+import { getMessaging, TokenMessage } from 'firebase-admin/messaging';
+
+// Note: this will only work in a live environment, not locally via the Firebase emulator.
+export const sendFCM = functions.https.onCall(
+  async (req: CallableRequest<{ message: TokenMessage; delay?: number }>) => {
+    const { message, delay } = req.data;
+    return await new Promise(() => {
+      functions.logger.info('Sleeping this many milliseconds: ' + (delay ?? 0));
+      setTimeout(async () => {
+        functions.logger.info('done sleeping');
+        const result = await getMessaging().send(message);
+        return { messageId: result };
+      }, delay ?? 0);
+    });
+  },
+);