Add support target_session_attrs

[AlexanderSabirov]

Problem

When specifying multiple hosts in a PostgreSQL cluster, it is possible to connect to the server in read-only mode.

Solution

When specifying multiple hosts in a PostgreSQL cluster, it is necessary to pass the parameter target_session_attrs. This PR adds support for that parameter.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[AlexanderSabirov]

Hello everyone!

I wanted to share a note about connecting to the PostgreSQL cluster. Because of our architecture, we can’t use a VIP or a load balancer for this.

Right now, if we list all the cluster hosts like host = server1,server2,server3, the connection will go to the first available server, even if it’s in read-only mode.

To fix this, I’ve added the target_session_attrs=read-write parameter in the Merge Request. This ensures that the connection only goes to a server that can handle read-write operations. You can find more details in the PostgreSQL docs: https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNECT-TARGET-SESSION-ATTRS.

@mikealfare
@colin-rogers-dbt
Could you please review the Merge Request when you have a moment?

Thanks!