Add Partial Support // Extraction and Apply Updates

[bryantgillespie]

Summary

Adds partial template extraction/apply support.

Partial templates can now scope exported/applied template data by collections/components, with relation handling strategies
for excluded collections.

Changes

• Add template plan metadata support for partial templates
• Add collection/component scoping flags
• Add deep schema/content expansion for related collections
• Add relation strategies:
  • deep
  • empty
  • preserve
• Add excluded relation warnings + apply-time guard
• Skip broken junction collections when FK targets are excluded
• Finalize collection/field metadata after schema load
• Improve error context around collection/data/relation load failures
• Remove dead update-required-fields path
• Add tests for template plans, metadata scoping, relation inclusion, junction detection

Validation

• npm run build passes
• Unit tests pass: 32 passing

Notes

• Lint currently fails repo-wide with many pre-existing issues; not fully addressed here.
• Test prerelease can is published and can be run with:

npx directus-template-cli@partials <command>

[LZylstra]

Really nice work on this. A few things to fix before merging, the most critical being an ordering bug with finalizeFields that'll break FK inserts on most real templates.