Add aria_custom_resource and related models

[davidfischer-ch]

Fix #8

• [x] Custom Resource Core
• [x] Properties
  • [x] Core property attributes
  • [x] Implement Default to/from API
  • [x] Test Default
  • [x] Integrate Properties to/from API inside Custom Resource to/from API
  • [x] Test with some content (in custom resource acceptance test -> especially nil value (undefined) and other subtle edge cases)
  • [x] Properties Ordering
  • [x] Implement OneOf to/from API
  • [x] Test OneOf
• [x] CRUD Actions
  • [x] Create Action
  • [x] Read Action
  • [x] Update Action
  • [x] Delete Action
  • [ ] Make Update Action optional?
• [ ] Additional Actions 🚧
• [ ] Custom Form inside (tm) ...
• [x] Update example in doc

Fix #18

• [x] Resource Action

[Towl]

Hello,

Here is an example that could be useful: https://stackoverflow.com/questions/25182923/serialize-a-map-using-a-specific-order

[Towl]

And this : https://pkg.go.dev/gitlab.com/c0b/go-ordered-json

[davidfischer-ch]

I finally made it! Both unit and acceptances tests are showing that ordering of properties is preserved!