Moderation charters system data contract (moderation teams C1) #4878

Part of #4865 (decentralized moderation teams). Item C1 of the PR split. Wave 1: no dependency, can start now.

Summary

A new system data contract for moderation charters. A team applies to moderate a contract by creating a charter document in it. The charter says how the team moderates, what it charges and how it splits the pay.

Decisions implemented: D1 (amended), D15, D29, D30, D34, D38, D50, D57, D58, D60 in #4865.

Current behaviour

System contracts live in their own packages (packages/dpns-contract, packages/document-history-contract, ...), are aggregated by packages/data-contracts, versioned in packages/rs-platform-version/src/version/system_data_contract_versions/, and created in state at the first block of the protocol version that introduces them. There is no charter contract.

Scope

• Package packages/moderation-charters-contract (name open) with a v1 JSON schema and the Rust crate, wired into data-contracts, the system contract versions, and the JS side the way feat(platform)!: document history system contract with per-doctype opt-in #4171 did for document history.
• Document type charter, immutable and undeletable (D60):
  • targetContractId, on a contested unique index so a create opens the election (D57); the index is marked as a moderation election so A3 sources the windows and fund from the target contract;
  • description: free text, at most 4096 bytes (D58);
  • abilities: the subset of delete, ban, suspend, warn the team claims, with a required power per ability (D9);
  • members: the initial membership with a power each, the applicant is the leader and is a member with a power (D28, D29, D30), at most 16 members;
  • reasonCodes: the code table, code to label (D50);
  • moderatorsAmounts: the moderators amount per moderated document type and per action (D45);
  • split: leader share, equal share, action-count share, three percentages summing to 100 (D34, D38).
• Pure-data validation of the charter lives in rs-dpp so consensus PRs can call it: percentages sum to 100, powers reachable by the listed members, abilities within the envelope of the target contract (checked by H2, not here).
• Ship the contract definition and registration. Do not add the first-block creation to perform_events_on_first_block_of_protocol_change in this PR; H2 adds it, so no contest can open before elections exist.

Out of scope

• Opening the poll (A3, H2), the seated team (H1).

Tests

• Schema fixture round-trips through rs-dpp and the JS contract test, like documentHistoryContract.spec.js.
• Validation refuses percentages not summing to 100, more than 16 members, a leader missing from the members, and a description over 4096 bytes.