feat: Add enum support with context-aware breaking change detection

[domdomegg]

Summary

Implements detection of JSON Schema enum changes with context-aware breaking change detection.

Resolves the issue where enum arrays being extended or reduced were not detected by the tool.

Changes

• Added EnumAdd and EnumRemove change types with context flags (lhs_has_no_enum and rhs_has_no_enum)
• Smart breaking change logic:
  • Adding values to existing enum: non-breaking (accepts more data)
  • Removing values from existing enum: breaking (rejects previously valid data)
  • Adding enum constraint entirely: breaking (restricts previously valid data)
  • Removing enum constraint entirely: non-breaking (accepts more data)
• Comprehensive test coverage: 9 test cases covering all scenarios including the real-world case from the issue

Examples

# Adding a value to existing enum (non-breaking)
$ json-schema-diff old.json new.json
{"path":"","change":{"EnumAdd":{"added":"debug","lhs_has_no_enum":false}},"is_breaking":false}

# Removing a value from existing enum (breaking)
$ json-schema-diff old.json new.json  
{"path":"","change":{"EnumRemove":{"removed":"debug","rhs_has_no_enum":false}},"is_breaking":true}

# Adding enum constraint (breaking)
$ json-schema-diff old.json new.json
{"path":"","change":{"EnumAdd":{"added":"error","lhs_has_no_enum":true}},"is_breaking":true}

# Removing enum constraint (non-breaking)
$ json-schema-diff old.json new.json
{"path":"","change":{"EnumRemove":{"removed":"error","rhs_has_no_enum":true}},"is_breaking":false}

Fixes #38

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

📋 Changelog Preview

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New Features ✨

• (release) Replace release bot with GH app by Jeffreyhung in #41

• Add enum support with context-aware breaking change detection by domdomegg in #46

• Add string validation support (pattern, minLength, maxLength) by domdomegg in #51
• Support format by brhutchins in #45
• Support custom ids and $defs from draft 2020-12 by cakemanny in #44

Internal Changes 🔧

Release

• Fix changelog-preview permissions by BYK in #54
• Switch from action-prepare-release to Craft by BYK in #52

Other

• Use pull_request_target for changelog preview by BYK in #53

Other

• Fix clippy lints by untitaker in #42

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[untitaker]

thanks and sorry for the delay! this slipped through the cracks