Document how to set up secure connections in Postgres Source docs

[grishick]

Users are not aware of how we enforce encryption in transit, so we should add an explanation of how we do that and which modes are allowed w/ and w/o SSH tunneling

[grishick]

Question for grooming: does it make sense (would it get us to a better result faster) if someone on the DBs & DWs team pairs up with @Amruta-Ranade to add documentation on setting up secure connections in Airbyte Cloud for

• Postgres Source (this ticket)
• Postgres Destination
• MySQL Source
• MySQL Destination

[Amruta-Ranade]

On it!

[Amruta-Ranade]

Addressed in https://github.com/airbytehq/airbyte/pull/16782