OSW-2388: Fix database connection pool exhaustion in ConsDB pqserver insert path.

[bbrondel]

This change fixes connection cleanup in the helper functions that cross reference exposure ID to day_obs/seq_num/[detector].

Two other bugs are also addressed, for a cached lookup and for a formatted print statement.

[Copilot]

Pull request overview

This PR addresses connection pool exhaustion in the pqserver insert path by ensuring DB sessions created via the get_db() generator are deterministically closed when used outside FastAPI’s dependency lifecycle. It also fixes a cached instrument schema lookup bug and corrects a logging statement to actually log the incoming SQL query.

Changes:

• Ensure InstrumentTable helper methods explicitly close the get_db() generator so sessions/connections are returned to the pool immediately.
• Fix get_instrument_list() to correctly populate and return the module-level cached _instrument_list.
• Fix pqserver query endpoint logging to log data.query using parameterized logging.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
python/lsst/consdb/handlers/external.py	Fixes query endpoint logging to correctly log the provided SQL query.
python/lsst/consdb/dependencies.py	Fixes instrument list caching by using the module-level _instrument_list.
python/lsst/consdb/cdb_schema.py	Ensures DB sessions from get_db() are properly closed in helper lookup paths to prevent connection leaks.

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[Vebop]

Definitely an improvement, please consider adding the context manager

[Vebop]

Why not a context manager here? That way the db connection always calls db_gen.close if there's an error on 189

from contextlib import contextmanager

@contextmanager
def _session(self):
    try:
        yield next(self.get_db)
    finally:
        self.get_db.close()

# Usage anywhere in the class:
with self._session() as db:
    query_result = db.execute(query).first()

(Apply this suggestion to the following two edits in this file too.)

[Vebop]

Suggested change