refactor: add observation module

[steve-chavez]

• Centralizes log traces into a single module. Which improves maintainability and removes some complexity from AppState.
• Will enable handling verbosity on log traces (required for feat: log connection pool events on log-level=info #3229)
• Might also help with opentelemetry (feat: produce OpenTelemetry traces with hs-opentelemetry #3140)
• Got the structure from Observability nikita-volkov/hasql-pool#40.

Next steps

• Move the messages from the Logger to Observation (showObservation).
• There are more improvements to make but it will involve changing the messages. Wanted to keep the behavior as is for now.

[steve-chavez]

Hm, the only test that is failing is:

def test_log_postgrest_version(defaultenv):
    "Should show the PostgREST version in the logs"

    with run(env=defaultenv) as postgrest:
        version = postgrest.session.head("/").headers["Server"].split("/")[1]

        assert (
            "Starting PostgREST %s..." % version
            in postgrest.process.stdout.readline().decode()
        )

$ postgrest-test-io -k test_log_postgrest_version

test/io/test_io.py::test_log_postgrest_version FAILED                                                                                                                             

Really weird that postgrest-run produces:

$ postgrest-run 
19/Feb/2024:16:11:42 -0500: Starting PostgREST 12.1 (160caaf)

And the io tests don't produce that log line. Is there a difference with postgrest-run? 🤔

[laurenceisla]

@steve-chavez I think it's the ... which is not included anymore at the end? It should be added to the code or removed from the tests.

According to the CI error, it does log it:

https://github.com/PostgREST/postgrest/actions/runs/7939142788/job/21678864120?pr=3232#step:4:303

AssertionError: assert ('Starting PostgREST %s...' % '12.1 (169c4a6)') in '17/Feb/2024:03:54:48 +0000: Starting PostgREST 12.1 (169c4a6)\n'

[steve-chavez]

Ahh, thanks a lot for that one @laurenceisla. That saved me a lot of time.

According to the CI error, it does log it:

Right, so it's included in the red text then.. that confused me.

[steve-chavez]

This looks ready to merge. There are codecov warnings but to clear those we need the recovery tests #1766.