Fix complex key bugs and allow custom key sorting

[gwardwell]

Description

Fixes

• In some cases, a key field would attempt to copy from a type that did not include it.
• In some cases, not all fields for all keys would be copied over when they fields were part of different complex keys.
• Value types erroneously received extend and their fields @external

Adds

• Users can now provide a custom key sorter.
• Users can now specify the federation version, either v1 or a valid v2.x version (examples: v2.1, v2.3, etc.). The default is still v2.0.

BREAKING CHANGE

The version is no longer supplied as an enum. It is now supplied as a string, with v1 or a valid v2.x version being accepted. Additionally, changes have been made to fix complex key schema generation. Users should take care to carefully validate their generated schema after updating.

Type of Change

• [x] Bug Fix
• [x] New Feature
• [x] Breaking Change
• [ ] Refactor
• [ ] Documentation
• [ ] Other (please describe)

Checklist

• [x] I have read the contributing guidelines
• [x] Existing issues have been referenced (where applicable)
• [x] I have verified this change is not present in other open pull requests
• [ ] Functionality is documented
• [x] All code style checks pass
• [x] New code contribution is covered by automated tests
• [x] All new and existing tests pass

[codecov[bot]]

Codecov Report

Merging #22 (c3aaa53) into main (2ec75fe) will increase coverage by 0.07%. The diff coverage is 96.92%.

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
+ Coverage   96.84%   96.91%   +0.07%     
==========================================
  Files          17       17              
  Lines         285      324      +39     
  Branches       88      106      +18     
==========================================
+ Hits          276      314      +38     
- Misses          9       10       +1     

Files Changed	Coverage Δ
src/schema/createLinkSchemaExtension.ts	72.72% <50.00%> (-9.10%)	:arrow_down:
src/schema/generateFroidSchema.ts	97.45% <98.33%> (+0.75%)	:arrow_up:
src/schema/constants.ts	100.00% <100.00%> (ø)