UUID as ID key for entities

[akeelnazir]

🚀 Changes proposed by this PR

The extension does not work for schema files that use uuid.UUID for ID fields. This fix checks for the flag AllowClientUUIDs and takes necessary action.

🔗 Related bug reports/feature requests

• fixes #69

🧰 Type of change

• [ X] Bug fix (non-breaking change which fixes an issue).
• [ ] New feature (non-breaking change which adds functionality).
• [ ] Breaking change (fix or feature that causes existing functionality to not work as expected).
• [ ] This change requires (or is) a documentation update.

📝 Notes to reviewer

🤝 Requirements

• [x] ✍ I have read and agree to this projects Code of Conduct.
• [x] ✍ I have read and agree to this projects Contribution Guidelines.
• [x] ✍ I have read and agree to the Developer Certificate of Origin.
• [x] 🔎 I have performed a self-review of my own changes.
• [x] 🎨 My changes follow the style guidelines of this project.
• [x] 💬 My changes as properly commented, primarily for hard-to-understand areas.
• [x] 📝 I have made corresponding changes to the documentation.
• [x] 🧪 I have included tests (if necessary) for this change.

[jordanfowler]

Given there is a concrete definition for what a UUID actually is defined by RFC 4122, it seems like ogen or this extension should know how to marshal [16]byte regardless of which library is being used to actually generate UUIDs. For reference:

// A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
// 4122.
type UUID [16]byte