MongoDB connector: add documentation/examples for connecting to an instance with user that has no permissions to connect to default database

[artem-shelkovnikov]

Problem Description

MongoDB has a special way to authenticate users: https://www.mongodb.com/docs/manual/core/security-scram/

In short, user is authenticated against a database. If no database is passed, user is authenticated to default database (admin), see https://www.mongodb.com/docs/manual/reference/connection-string/#standard-connection-string-format.

In case a readonly user is created, that has access only to database that user wants to sync, for example foo_database, this user can only authenticate against this DB. In practice it means, that in connector user needs to specify their host like this:

mongodb://hostname:port/foo_database

It's not clear and not obvious, so we need to add documentation and other UI hints to make it clear.

Proposed Solution

1. Add this information into our official MongoDB documentation
2. Maybe add a tooltip for host?