feat: introduce holder capabilities

[nanderstabel]

Description of change

This PR adds Holder functionality to UniCore.

• UniCore is now able to both send Credential Offers to a target_url as well as well as listen for incoming Credential Offers in order to (after confirmation) Accept or Reject the offer.
• Refactoring of agent_api_rest
• Abstracted Custom Query code into agent_shared
• Refactored test_utils across sub modules for test re-usability utilizing rstest

Links to any relevant issues

fixes #111

How the change has been tested

Tested through new and existing (adjusted) unit tests as well as updated Postman Collection.

How to test this flow manually using the Postman Collection:

1. (Issuer): Hit the Issuance/w3c_vc_credentials request
2. (Issuer): Hit the Issuance/offers request
3. (Issuer): Hit the Issuance/offers_send request (this will send the Credential Offer to UniCore's new Holder module)
4. (Holder): Hit the Holder/offers request
   • (Holder): Hit the Holder/offers_accept request:
     • (Holder): Hit the Holder/credentials request to see the received Credential
   • (Holder): Or hit the Holder/offers_reject request:

Definition of Done checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• 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
• I have successfully tested this change in a docker environment

[daniel-mader]

Looks like a well-functioning first iteration of the "holder role" 👍 I could not fully assess all technical refactorings, paired with new features - but I like the comments and tests to assert functionality and prevent bugs.

[daniel-mader]

Awesome! All three major roles of SSI are now implemented in UniCore! 🥳

[github-actions]

🎉 This PR is included in version 1.0.0-beta.1 🎉

The release is available on GitHub release

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[github-actions]

🎉 This PR is included in version 1.0.0-alpha.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀