[keyserver] Replace deprecated sendToDevice firebase-admin method

Summary: This method is deprecated and is now completely failing all requests. This diff resolves [ENG-235](https://linear.app/comm/issue/ENG-235/update-fcm-code-to-not-use-legacy-methods).

Test Plan:
I set up a test environment on my personal server. It's running the latest keyserver release (115). In this environment, I created a [test script](https://linear.app/comm/issue/ENG-9323/android-notifications-are-completely-broken#comment-516bbedd) to generate some notifs by sending messages from commbot to a test account. I confirmed that the test account received a notif on an Android device it's logged into.

I also did some testing to make sure the error handling logic worked correctly. In my test environment, I set the device token to `fake` and checked what the error response looked like, and made sure that `error.errorInfo.code` contained the error code. For my fake device token, the error code ended up being `messaging/invalid-argument`, but I'm pretty sure that the error code would appear in the same place for the types of errors we care about (`fcmTokenInvalidationErrors`).

Reviewers: varun, will

Reviewed By: varun, will

Subscribers: marcin, kamil, tomek

Differential Revision: https://phab.comm.dev/D13368

keyserver/flow-typed/npm/firebase-admin_vx.x.x.js

@@ -22,11 +22,7 @@ declare module 'firebase-admin' {
   };
 
   declare export type FirebaseMessaging = {
-    +sendToDevice: (
-      deviceToken: string,
-      notification: Object,
-      options: Object,
-    ) => Promise<FirebaseDeliveryResult>,
+    +send: (notif: Object) => Promise<string>,
     ...
   };
 

keyserver/package.json

@@ -61,7 +61,7 @@
     "express": "^4.17.3",
     "express-ws": "^4.0.0",
     "file-type": "^12.3.0",
-    "firebase-admin": "^10.1.0",
+    "firebase-admin": "^12.5.0",
     "geoip-lite": "^1.4.5",
     "invariant": "^2.2.4",
     "landing": "0.0.1",

keyserver/src/push/utils.js

@@ -142,12 +142,16 @@ async function fcmPush({
   for (let i = 0; i < results.length; i++) {
     const pushResult = results[i];
     for (const error of pushResult.errors) {
-      errors.push(error.error);
-      const errorCode =
-        error.type === 'firebase_error'
-          ? error.error.errorInfo.code
-          : undefined;
-      if (errorCode && fcmTokenInvalidationErrors.has(errorCode)) {
+      errors.push(error);
+      if (
+        error &&
+        typeof error === 'object' &&
+        error.errorInfo &&
+        typeof error.errorInfo === 'object' &&
+        error.errorInfo.code &&
+        typeof error.errorInfo.code === 'string' &&
+        fcmTokenInvalidationErrors.has(error.errorInfo.code)
+      ) {
         invalidTokens.push(targetedNotifications[i].deliveryID);
       }
     }
@@ -171,12 +175,9 @@ async function fcmPush({
   return result;
 }
 
-type FCMSinglePushError =
-  | { +type: 'firebase_error', +error: FirebaseError }
-  | { +type: 'exception', +error: mixed };
 type FCMSinglePushResult = {
   +fcmIDs: $ReadOnlyArray<string>,
-  +errors: $ReadOnlyArray<FCMSinglePushError>,
+  +errors: $ReadOnlyArray<mixed>,
 };
 async function fcmSinglePush(
   provider: FirebaseApp,
@@ -185,21 +186,14 @@ async function fcmSinglePush(
   options: Object,
 ): Promise<FCMSinglePushResult> {
   try {
-    const deliveryResult = await provider
-      .messaging()
-      .sendToDevice(deviceToken, notification, options);
-    const errors = [];
-    const ids = [];
-    for (const fcmResult of deliveryResult.results) {
-      if (fcmResult.error) {
-        errors.push({ type: 'firebase_error', error: fcmResult.error });
-      } else if (fcmResult.messageId) {
-        ids.push(fcmResult.messageId);
-      }
-    }
-    return { fcmIDs: ids, errors };
+    const fcmMessageID = await provider.messaging().send({
+      ...notification,
+      token: deviceToken,
+      android: options,
+    });
+    return { fcmIDs: [fcmMessageID], errors: [] };
   } catch (e) {
-    return { fcmIDs: [], errors: [{ type: 'exception', error: e }] };
+    return { fcmIDs: [], errors: [e] };
   }
 }
 
@@ -211,7 +205,7 @@ async function getUnreadCounts(
   const query = SQL`
     SELECT user, COUNT(thread) AS unread_count
     FROM memberships
-    WHERE user IN (${userIDs}) AND last_message > last_read_message 
+    WHERE user IN (${userIDs}) AND last_message > last_read_message
       AND role > 0
       AND JSON_EXTRACT(permissions, ${visPermissionExtractString})
       AND JSON_EXTRACT(subscription, ${notificationExtractString})