Auto-include partition columns in unique indexes (GH-3557)

[jeremydmiller]

Summary

• Fixes Add functionality to allow custom indexes with multiple fields including meta data  #3557 - PostgreSQL requires unique indexes on partitioned tables to include all partitioning columns
• Adds logic in Weasel's IndexDefinition.correctedExpression() to automatically append any missing partition columns when generating DDL for unique indexes on partitioned tables
• Uses a local Weasel project reference with the fix (the Weasel change needs to be published as a new package version before merging)

Weasel Change

The core fix is in Weasel's IndexDefinition.cs (correctedExpression(Table? parent)). When IsUnique and the parent table has a Partitioning strategy, any partition columns not already present in the index's Columns are appended to the index expression. The Weasel commit is on branch GH3557-unique-index-partitioning at ~/code/weasel.

Tests Added

• unique_index_on_partitioned_table_includes_partition_columns_in_ddl - DDL includes tenant_id for hash-partitioned table
• unique_index_on_soft_delete_partitioned_table_includes_partition_columns_in_ddl - DDL includes mt_deleted for soft-delete partitioned table
• unique_index_does_not_duplicate_partition_columns_already_present - No duplication when partition column already in index via TenancyScope.PerTenant
• unique_index_on_partitioned_table_can_be_applied_to_database - Integration test applying schema to PostgreSQL

Test plan

• All 25 partitioning tests pass
• All 6 unique index tests pass
• All 8 multi-tenancy partitioning tests pass
• Weasel change needs to be committed/published separately before switching back to NuGet reference

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