Implement error handling and OID4VC Error Responses

[nanderstabel]

Description

The use of anyhow errors should be deprecated and replaced with thiserror for proper error handling.

For each Spec the corresponding Error Responses should be implemented:

• OpenID4VCI:
  • Token Error Response
  • Credential Error Response
• OpenID4VP:
  • Error Response
• SIOPv2:
  • Self-Issued OpenID Provider Error Response

Furthermore, all library specific errors should be handled properly as well.

Motivation

This will improve DX in downstream code and adds better spec compatibility

Resources

See description

To-do List

• Implement thiserror
• Implement spec-specific Error Responses