feat: initialize Nonce endpoint

[coplat]

Description of change

This PR initializes the nonce endpoint as described in OID4CI's draft 15 specification. . This is vital as a means to prevent replay attacks during credential requests. Nonces are generated when a post request is made to the /oid4vci/nonce endpoint, returning a unique and fresh c_nonce.

This c_nonce must then be included in the proof of a CredentialRequest made to the issuer. If that nonce has already been redeemed or does not exist, the credential request is denied.

If it is valid, the c_nonce is then marked as redeemed and can no longer be reused.

This PR initializes the nonce endpoint which generates the nonce, and validates the nonce when a credential request is made within the API layer. Further, the nonce commands, events, errors and corresponding aggregate are also initialized within this PR.

Links to any relevant issues

• Blocked by fix: retain Presentation layer during decoding to allow nonce extraction openid4vc#115

How the change has been tested

Existing tests have been updated to include nonces. Nonce endpoint has been added to the postman collection for c_nonce generation.

Definition of Done checklist

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• I have followed the contribution guidelines for this project
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• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
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