Credentials to connect to your MongoDB instance. You might have to get the credentials from a team member.
NOTE: While setting this value in the Production and Staging environments on Github, make sure to include the value within double quotes and escape any characters using \ as necessary. If you don't set this correctly, your deployment will fail.
This usually looks something like this:
MONGO_AUTH_CREDENTIALS="mongodb+srv://USER_NAME:PASSWORD@COLLECTION_NAME.uocfg.mongodb.net/DATABASE_NAME?retryWrites=true&w=majority"