fix(postgresql): parsing bug with expression based unique indexes on postgres

[luis-dfns]

Fixes a bug where the unique key violation parsing incorrectly returns extra "comma" characters for expression based unique indexes such as:

CREATE UNIQUE INDEX "unique_idx" ON "table_name"(
  "column_1",
  (column_2->>'field'),
);

In which case the columns affected would previously be returned as ["column_1,"] instead of ["column_1"]

[Copilot]

Pull request overview

This PR fixes a bug in parsing unique constraint violation errors for PostgreSQL when the constraint involves expression-based indexes. The issue occurs when parsing the error detail message to extract field names from expressions like json_data->>'field'.

Changes:

• Modified the parsing logic to use splitn(2, " (") instead of split(" (") to correctly handle expressions containing parentheses
• Added test coverage for expression-based unique indexes on PostgreSQL
• Changed quote character from escaped to raw string format for improved readability

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
quaint/src/connector/postgres/error.rs	Fixed parsing logic to handle expression-based unique indexes by using splitn(2) and simplified quote escaping
quaint/src/tests/query/error.rs	Added comprehensive test case for expression-based unique indexes with JSONB field extraction

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[CLAassistant]

All committers have signed the CLA.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing luis-dfns:main (0559d36) with main (7f62a0e)}

Summary

✅ 11 untouched benchmarks
⏩ 11 skipped benchmarks¹

Footnotes

1. 11 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[jacek-prisma]

Hi @luis-dfns!
Thanks for the contribution.
Looks like the newly added test is failing in CI.

[luis-dfns]

hi @jacek-prisma ! I had some trouble executing the tests locally, but it should work now