Give warning when there are no unique constraints on one-to-one columns

[goldenice]

No description provided.

[Copilot]

Pull Request Overview

This PR adds validation warnings for one-to-one relationships that lack unique constraints or unique indexes on the foreign key column. Without these constraints, the database cannot enforce the one-to-one cardinality, potentially allowing the relationship to become many-to-one.

Key Changes:

• Added logic to detect missing unique constraints/indexes on one-to-one relationship columns
• Introduced new warning code ORM-SV-3104 with descriptive messaging
• Added comprehensive test coverage for the new validation scenario

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/tools/validateSchema.ts	Implements the unique constraint/index check for one-to-one columns
src/errors/SchemaValidationError.ts	Defines the new ORM-SV-3104 warning code and associated messages
tests/pg-backend/validateSchema.test.ts	Adds three test cases covering scenarios with and without unique constraints

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