Implement support for PG18 PERIOD

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Closes #3710

[Copilot]

Pull request overview

This pull request implements support for PostgreSQL 18's PERIOD feature for foreign keys with temporal tables, closing issue #3710. The PERIOD feature allows foreign keys to reference temporal data by treating the last column (which must be a range type) as a temporal period, enabling proper referential integrity for time-based relationships.

Changes:

• Added WithPeriod() extension methods for configuring foreign keys with the PERIOD feature
• Implemented validation to ensure PERIOD is only used with PostgreSQL 18+, requires the principal key to have WITHOUT OVERLAPS, and requires the last column to be a range type
• Extended migration SQL generation to produce correct PERIOD syntax in foreign key constraints
• Added scaffolding support to detect and preserve PERIOD annotation when reverse-engineering databases

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/EFCore.PG/Extensions/BuilderExtensions/NpgsqlForeignKeyBuilderExtensions.cs	New file providing WithPeriod() fluent API methods for configuring foreign keys
src/EFCore.PG/Extensions/MetadataExtensions/NpgsqlForeignKeyExtensions.cs	New file with metadata extension methods for getting/setting PERIOD annotation
src/EFCore.PG/Metadata/Internal/NpgsqlAnnotationNames.cs	Added Period annotation constant
src/EFCore.PG/Metadata/Internal/NpgsqlAnnotationProvider.cs	Added annotation propagation for foreign key constraints with PERIOD
src/EFCore.PG/Infrastructure/Internal/NpgsqlModelValidator.cs	Added validation for PERIOD feature requirements (version, range type, WITHOUT OVERLAPS on principal)
src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs	Overrode ForeignKeyConstraint to generate proper PERIOD syntax in SQL
src/EFCore.PG/Scaffolding/Internal/NpgsqlDatabaseModelFactory.cs	Added detection of conperiod field when scaffolding foreign keys
src/EFCore.PG/Properties/NpgsqlStrings.resx	Added error message resources for PERIOD validation, plus whitespace cleanup
src/EFCore.PG/Properties/NpgsqlStrings.Designer.cs	Generated code for new error message accessors
test/EFCore.PG.Tests/Infrastructure/NpgsqlModelValidatorTest.cs	Added test for WITHOUT OVERLAPS validation on PERIOD foreign keys
test/EFCore.PG.FunctionalTests/Migrations/MigrationsNpgsqlTest.cs	Added tests for creating and altering foreign keys with PERIOD

Files not reviewed (1)

• src/EFCore.PG/Properties/NpgsqlStrings.Designer.cs: Language not supported

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[Copilot]

Pull request overview

Copilot reviewed 12 out of 13 changed files in this pull request and generated 2 comments.

Files not reviewed (1)

• src/EFCore.PG/Properties/NpgsqlStrings.Designer.cs: Language not supported

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