Moderators warn users: on-chain warning record (moderation teams D) #4879

Part of #4865 (decentralized moderation teams). Item D of the PR split. Wave 1, in progress.

Summary

Moderators can warn a user: an on-chain record with no consensus effect and no expiry, like a document removal record. In scope for protocol version 14.

Decisions implemented: D49 in #4865.

Current behaviour

ContractUserModerationAction in packages/rs-dpp/src/state_transition/state_transitions/contract/contract_user_moderation_transition/v0/mod.rs has ban, unban, suspend and unsuspend. Nothing records a warning.

Scope

• A Warn action on the user moderation transition, carrying the target identity and a ContractModerationReason (text plus optional code), so the reason-code check (E) and the action counters (H3b) can plug in later.
• A warnings record under the contract, keyed by identity, holding every warning with its reason, the moderator and the block time. Warnings never expire and are never removed.
• A query and proof for the warnings of an identity in a contract, through DAPI, the proof verifier and rs-sdk, like the banlist queries.
• Fees and the actor gate exactly as for the other actions.

Coordination

• Pick the key in the contract's "other" tree (packages/rs-drive/src/drive/contract/paths.rs, keys 16, 32, 64, 96, 128 and 192 are taken) now; H1 takes the next free one.
• Error codes stay in the 411xx moderation band; StateError variants are append-only.
• H3a (membership) and G (co-signing) add to the same action enum; merge this first.