Add support for unix domain sockets (and peer authentication)

[mpilquist]

Adds support for connecting to the Postgres server via unix domain sockets.

Example usage:

Session.Builder[IO]
  .withUnixSockets
  .withUser("jimmy")
  .withDatabase("world")
  .single

The above configuration results in connecting via /tmp/.s.PGSQL.5432. Variations of withUnixSockets are supplied for customizing the path.

Supports both trust and peer authentication types.

TODO: Figure out how to test this with the current docker-compose based configuration

[mpilquist]

I tried adding a test in c521068 but it fails on Mac w/ Colima due to permissions issues. The new container fails to start with this error:

025-03-25 12:57:24.774 UTC [49] LOG:  could not set permissions of file "/var/run/postgresql/.s.PGSQL.5432": Invalid argument
2025-03-25 12:57:24.774 UTC [49] WARNING:  could not create Unix-domain socket in directory "/var/run/postgresql"
2025-03-25 12:57:24.774 UTC [49] FATAL:  could not create any Unix-domain sockets
2025-03-25 12:57:24.782 UTC [49] LOG:  database system is shut down

Tried various things (e.g. changing fstype used by Colima, symlink nonsense, etc) without luck.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 52.17391% with 11 lines in your changes missing coverage. Please review.

Project coverage is 83.24%. Comparing base (a2c4f74) to head (7ca500b). Report is 197 commits behind head on main.

Files with missing lines	Patch %	Lines
modules/core/shared/src/main/scala/Session.scala	50.00%	11 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1192      +/-   ##
==========================================
- Coverage   83.94%   83.24%   -0.70%     
==========================================
  Files         138      140       +2     
  Lines        2136     2238     +102     
  Branches      243      230      -13     
==========================================
+ Hits         1793     1863      +70     
- Misses        343      375      +32     

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