Implement Claim Publisher database functionalities

[GMKrieger]

📚 Context

The input reader update (#348) was meant solely for the input reader, and did not take any other service into consideration.

The claim publisher will need additional support to execute its task, and the repository needs to be updated beforehand to accommodate this. We will need to create additional tables, relations, constraints, as well as implement ways to interact with this information in a safe and atomic way.

It's important to bring attention to how we interact with the data to keep the database consistent, as some transactions are only valid if all the parts move accordingly.

✔️ Solution

The claim publisher functionalities do not require an update on the database model, as of the moment of writing this issue (2024-06-25).

The claim publisher will need to get the latest claim generated by the validator after finishing an epoch, and all associated proofs. This is the only functionality the Claim Publisher requires from the database.

📈 Subtasks

• Implement necessary repository functions
• Create tests for the new functions

[GMKrieger]

This issue is obsolete with #493, as the Claim Publisher will no longer exist.