feat: inline pg-type-mappings plugin into graphile-settings

[pyramation]

Summary

Inlines the graphile-pg-type-mappings plugin from the main branch into graphile-settings as a PostGraphile v5 preset. This plugin maps custom PostgreSQL types to GraphQL scalar types.

Default mappings:

• email, hostname, url, origin → String

The v4 plugin used builder.hook() patterns. This v5 conversion uses:

• gather.hooks.pgCodecs_findPgCodec to create codecs for custom types
• schema.hooks.init to map codecs to GraphQL types

Updates since last revision

• Removed single_select and multiple_select types - These JSONB domain types have been removed from the type mappings as they are no longer needed
• Renamed smart comments - All domain type comments changed from @name pgpmInternalType* to @name constructiveInternalType*
• Simplified domain type validation - Removed heavy regex validation from all domains:
  • email: now just citext (no regex - real validation is email confirmation)
  • hostname: now just text (no regex - real validation is DNS resolution)
  • url, origin, attachment: now just text (no regex)
  • image: jsonb requiring only url key (removed mime requirement and URL regex)
  • upload: jsonb requiring at least one of url, id, or key (removed mime requirement and URL regex)
• Updated fixtures - The __fixtures__/sqitch/simple-w-exts/extensions/@pgpm/types/ directory updated to match

Companion PR: constructive-db#469 contains the corresponding database-side changes.

Review & Testing Checklist for Human

• Coordinate merge timing - This PR and constructive-db#469 must be merged together to avoid mismatched type definitions
• Verify no production usage of single_select/multiple_select - These domain types are being removed; ensure no existing databases depend on them
• Review simplified validation impact - The removal of regex validation means previously rejected values will now be accepted. Verify this is intentional and application-layer validation exists where needed
• Test upload domain change - The upload domain now accepts id or key as alternatives to url. Verify this aligns with how uploads are used in the application
• Test with actual PostgreSQL types - Create a table with an email domain type and confirm it appears as String in the GraphQL schema

Recommended test plan:

1. Create a test database with the simplified domain types
2. Insert values that would have failed the old regex validation (e.g., unusual but valid emails)
3. Verify the GraphQL schema correctly maps these types to String
4. Test upload domain with {"id": "123"} and {"key": "abc"} objects

Notes

The original v4 plugin source was retrieved from origin/main:graphile/graphile-pg-type-mappings/src/index.ts. The standalone package directory on develop-v5 only contained dist/ and node_modules/ (no source).

Link to Devin run: https://app.devin.ai/sessions/ba45b64c92bb4307bf9e920123213d9e
Requested by: Dan Lynch (@pyramation)

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✅ Devin Review: No Issues Found

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