feat: contract acceptance publication

[mrnaveira]

Description

• New gRPC method in the validator node for publishing a contract acceptance,
  • The only parameter for now is the contract_id
  • The validator node internally uses its own public key for building the acceptance.
  • The signature of the acceptance only has a mock value for now. When we have contract constitutions in place, we probably would want it to be the signature of a hash of a contract constitution identification.
  • Calls the new gRPC method in the wallet to publish the transaction
• New gRPC method in the wallet to submit a contract acceptance. It builds and sends to the network a contract acceptance with the corresponding flags and features

Motivation and Context

Validator nodes need to be able to publish contract acceptances, for contracts in which they are included as committee members.

This PR continues previous work and provides a gRPC method in the validator node (and a corresponding one in the wallet) to publish contract acceptances.

The functionality can be used in future work for implementing both auto-acceptance and manually acceptance of contract constitutions.

How Has This Been Tested?

New integration test that publishes and mines a contract acceptance through the new validator node gRPC endpoint

[SWvheerden]

This looks good.
The only thing missing here, ut this could be a follow up PR, is validation on these transactions.
All the stuff the base node needs to check

[mrnaveira]

This looks good. The only thing missing here, ut this could be a follow up PR, is validation on these transactions. All the stuff the base node needs to check

Correct. The work on layer 2 so far was intended to have a way to store all the features into the blockchain. We left the consensus rules/validation for future PRs, but it's something we will need to address soon.

[sdbondi]

Looks good, few minor comments