feat: add Batch Credential Endpoint

[nanderstabel]

Description of change

Support for the OpenID4VCI Batch Credential : credential

Notable changes:

• support for batch credential request for both Wallet and CredentialIssuer (Server).
• Regarding the OpenID4VCI extension points: CredentialFormats now needs a generic type (default is WithParameters:

pub enum CredentialFormats<C = WithParameters>
where
    C: FormatExtension + DeserializeOwned,

This ensure that any datatype that has a format field, also includes a credentialformat-specific field(s). E.g. for jwt_vc_json there need to be a credential_definition field.

However, in the (batch) credential response, instead of this additional credentialformat-specific field(s) there needs to be a credential field with a credentialformat-specific Credential. In this case the additional generic type for CredentialFormats needs to be CredentialFormats<WithCredential>. At the moment this type is still defaulted to serde_json::Value for all credential formats, but this will change in the future.

Links to any relevant issues

fixes #50

How the change has been tested

The Batch Credential Flow is tested in oid4vc-manager/tests/oid4vci/pre_authorized_code.rs.
By using:

#[rstest::rstest]
#[case(false)]
#[case(true)]

oid4vc-manager/tests/oid4vci/pre_authorized_code.rs now test both single credential flow and batch credential flow.

Serializing is tested in: oid4vci/src/credential_response.rs

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