Add a timeout to mongoldb connections (#15258)

* Add option to set a socket timeout for mongodb requests

* Handle mongodb timeouts better

* add default to config

config.json.example

@@ -37,6 +37,7 @@
   "NODE_DB_URI": "mongodb://localhost:27017/habitica-dev?replicaSet=rs",
   "TEST_DB_URI": "mongodb://localhost:27017/habitica-test?replicaSet=rs",
   "MONGODB_POOL_SIZE": "10",
+  "MONGODB_SOCKET_TIMEOUT": "20000",
   "NODE_ENV": "development",
   "PATH": "bin:node_modules/.bin:/usr/local/bin:/usr/bin:/bin",
   "PAYPAL_BILLING_PLANS_basic_12mo": "basic_12mo",