Raw model fields, full encoding support, roundtrip encoding tests

[infinisil]

• Raw model fields and full encoding support

  This commit extends the model with a "raw field" abstraction, which allows parametrizing the fully-decoded model by whether some fields contain the raw encoded data or not.

  This makes a lot of things nicer:

  • We can now have a function that turns model types without the raw fields into one that does, but doesn't do any other encoding.
  • We can generate well-behaved Arbitrary instances for the model without the raw fields
  • The above two points combined let us generate test model types, encode its raw fields, then verify it (which requires the raw fields)

  As part of this, this commit also cleans up and fully implements the decoding and encoding of such raw data fields, by creating new Crypto.Fido2.Model.Binary.{Encoding,Decoding} modules, which contain functions for encoding/decoding all binary fields of the model

• Small model adjustments

  When trying to do roundtrip tests for the model encoding, these updates were necessary:

  • Make ccdCrossOrigin a required field. It not being set is the same as the value False
  • Comment out arcTransports. It was not used, as the webauthn-json library doesn't propagate that field

• Fully implement Arbitrary instances for Model types

• Add test for model encoding roundtrips

[infinisil]

TODO:

• [x] Comments
• [x] Roundtrip tests for encoding/decoding of the model types

[infinisil]

I updated the Binary.{Encoding,Decoding} modules to only export the functions that are necessary, and document them properly. Also added specs for the implementations as suggested