feat: add invitation list endpoint with query params

Description

Adding an endpoint for fetching all invitations with filters for state and role. Additional changes were necessary:

• Extending the create invitations to return more fields.
• Add Accept invitation request as previously it was using the create invitation response, which does not match to what we want to accept.
• Making optional id in the base record as not every response should have the "id" field.

Related issues

Testing

Manual

Checklist

• I have updated the documentation (if necessary)
• I have added unit tests for new functionality (if applicable)
• My code follows the style guidelines of this project
• I have tested this code on my local machine before submitting this MR

Reviewers

@boyan.tsolov @alexey.lunin

Additional Notes

Closes #65 (closed)