fix(env): try FIREBASE_CONFIG json when GCLOUD_PROJECT unset

Author: leomp12

functions/__env.js

@@ -1,14 +1,19 @@
 // setup server and app options from Functions config (and mocks)
-const { GCP_PROJECT, GCLOUD_PROJECT } = process.env
-const projectId = GCP_PROJECT || GCLOUD_PROJECT
+const { GCLOUD_PROJECT, FIREBASE_CONFIG, FUNCTION_REGION } = process.env
 const { pkg, server } = require('firebase-functions').config()
+
+let projectId = GCLOUD_PROJECT
+if (FIREBASE_CONFIG) {
+  projectId = JSON.parse(FIREBASE_CONFIG).projectId
+}
+const region = FUNCTION_REGION || 'us-central1'
 const functionName = server.functionName || 'app'
 
 module.exports = {
   functionName,
   operatorToken: server && server.operator_token,
   baseUri: (server && server.base_uri) ||
-    `https://us-central1-${projectId}.cloudfunctions.net/${functionName}`,
+    `https://${region}-${projectId}.cloudfunctions.net/${functionName}`,
   hostingUri: `https://${projectId}.web.app`,
   pkg: {
     ...pkg