feat: Adding a connection pool to reduce the time spent opening connection to Postgres

[Ma77Ball]

What changes were proposed in this PR?

This PR adds a HikariCP connection pool to SqlServer.scala so that jOOQ queries borrow pre-authenticated connections from a pool instead of opening a new TCP connection and performing SCRAM-SHA-256 authentication on every database call.

What changed in SqlServer.scala:

• Added a HikariConfig with maximumPoolSize=10, minimumIdle=2, connectionTimeout=30s, idleTimeout=10min, maxLifetime=30min (chosen to stay below typical PostgreSQL idle and load-balancer connection-reaping windows)
• Initialized a HikariDataSource and built the jOOQ DSLContext via DSL.using(dataSource, SQL_DIALECT) so queries draw from the pool
• Added a close() method to shut down the pool on application or test teardown, and updated clearInstance() to call it, so test classes that replace the singleton don't leak pool threads
• Added a documented warning against caching the DSLContext in a val or lazy val. MockTexeraDB swaps the singleton between test classes, and a cached context would hold a stale reference to a dead pool

Any related issues, documentation, discussions?

closes: #4852

How was this PR tested?

• Existing unit and integration tests pass — the pool-backed DSLContext is a drop-in replacement for the previous direct-driver context
• Verified the MockTexeraDB flow still works across test classes by running the full test suite and confirming no "Connection refused" failures from stale contexts

Was this PR authored or co-authored using generative AI tooling?

Co-authored with Claude opus 4.6 (Anthropic) in compliance with ASF

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 42.17%. Comparing base (056e39d) to head (c37711b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #4851   +/-   ##
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  Coverage     42.16%   42.17%           
  Complexity     2180     2180           
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  Files           980      980           
  Lines         36305    36297    -8     
  Branches       3783     3783           
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  Hits          15309    15309           
+ Misses        20068    20060    -8     
  Partials        928      928           

Flag	Coverage Δ
access-control-service	39.53% <ø> (ø)
computing-unit-managing-service	0.00% <ø> (ø)
config-service	0.00% <ø> (ø)
file-service	33.24% <ø> (ø)
workflow-compiling-service	47.72% <ø> (ø)

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[Yicong-Huang]

Looks good to me! Left inline comments

[Yicong-Huang]

please also change the title. this is not a refactor. we are adding a new feature.

[Yicong-Huang]

the latest version is HikariCP-7.0.2, any particular reason to stay on v5.1.0?