[Feature]: Support for decoding unassigned simple values

[anweiss]

Is there an existing issue for this?

• I have searched the existing issues

Description

When decoding CBOR data that contains unassigned simple values, as in those that aren't of false, true, null or undefined, an error is thrown:

ciborium/ciborium/src/de/mod.rs

Line 191 in 9a45110

h @ Header::Simple(..) => Err(h.expected("known simple value")),

A minimal repro was posted by @Anrock at anweiss/cddl#90 (comment).

It would be great to be able to capture these values so that CDDL tools can validate these values.

Acceptance Criteria

No response

Suggestions for a technical implementation

No response

[Anrock]

@dpal is there any plans to implement this? anweiss/cddl is almost the only cddl-tool in a good shape and having such breakers in it is a pity