SHUTTLE REVOLUTIONIZES EVENT HANDLING WITH POWERFUL NEW CALLBACKS!

Groundbreaking feature empowers developers to customize on-chain event processing, enhancing flexibility and control in the digital ecosystem.

Commit Details:

feat(shuttle): Support event level callback in shuttle (#2271) ## Why is this change needed? Support event level callbacks in Shuttle. This allows flexibility in skipping event processing if desired, and custom handling for onchain events and username proofs. ## Merge Checklist _Choose all relevant options below by adding an `x` now or at any time before submitting for review_ - [x] PR title adheres to the [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/) standard - [x] PR has a [changeset](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#35-adding-changesets) - [x] PR has been tagged with a change label(s) (i.e. documentation, feature, bugfix, or chore) - [ ] PR includes [documentation](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#32-writing-docs) if necessary. <!-- start pr-codex --> --- ## PR-Codex overview This PR adds support for event level callbacks in the shuttle package. ### Detailed summary - Added `OnChainEventRow` type to `db.ts` - Updated `HubEventProcessor` to support event level callbacks - Added `onHubEvent` method to `MessageHandler` - Added migration script for `onchain_events` table - Updated `App` class to handle `MergeOnChainHubEvent` events > ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}` <!-- end pr-codex -->