Draft and discuss schema changes for VerA v2

[marcocastignoli]

This issue serves as a collaborative space to draft and discuss proposed updates for the VerA schema v2.

Proposed changes:

1. Handle better verifications from same verifier but with different version: There are cases in which for the same compilation_id and deployment_id, a more recent version of the same verifier can find a better verified_contract. This cases are not currently supported by VerA because we follow the policity "always insert, never update" and the better entries are in conflicts with existing verified_contracts's unique constraint. Read more here: Find a solution for UNIQUE constraint blocking re‑verification of contracts originally verified by a buggy Sourcify server argotorg/sourcify#2089
2. Add code.keccak_normalized_code, so it will be possible to compare similar bytecodes with the same executional bytecodes but different immutables, libraries, auxdata, constructor arguments, ecc..
3. Add additional_input column to compiled_contracts, see Add new additional_input field in VerA argotorg/sourcify#2001
4. Consider adding a proxy_info table: Integrate proxy detection into the verification flow argotorg/sourcify#1712
5. Consider adding platform binaries to compiled_contracts: (e.g. linux, darwin) Input validation in APIv2 preventing from verifying Vyper versions lower than 0.3.2 argotorg/sourcify#2247 (comment)
6. Duplicate verifications by different verifiers: Add created_by to the unique constraint of verified_contracts such that the same verification can be added by multiple verifiers.

Blocked by

Adding migrations to verifier-alliance/database-specs. we should maintain migrations to better support schema upgrades. See #31 Done.