refactor(zetacore): delete ballots after maturity

[kingpinXD]

Description

Closes https://github.com/zeta-chain/node/issues/942

How Has This Been Tested?

• [ ] Tested CCTX in localnet
• [ ] Tested in development environment
• [ ] Go unit tests
• [ ] Go integration tests
• [ ] Tested via GitHub Actions

Summary by CodeRabbit

• New Features

  • Added functionality to delete matured ballots, enhancing ballot lifecycle management.
  • Introduced a new VoterList message type to track individual voter details.
  • Added event handling for deleted ballots to improve system responsiveness.

• Bug Fixes

  • Enhanced logic for managing observer rewards and matured ballots.

• Tests

  • Expanded test coverage for ballot deletion and voter list generation, ensuring robustness in functionality.

• Documentation

  • Updated changelog to reflect the latest changes and features.

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Walkthrough

The changes introduced in this pull request focus on enhancing ballot management within the system, specifically addressing the deletion of matured ballots. This includes the addition of new message types, modifications to existing functions for handling ballots, and the introduction of event emissions upon ballot deletion. The updates aim to streamline the lifecycle management of ballots, ensuring that matured ballots are efficiently removed from the state to optimize resource use.

Changes

Files	Change Summary
changelog.md	Added entry for deleting ballots after they mature.
proto/zetachain/zetacore/observer/ballot.proto	Introduced VoterList message with fields for voter address and vote type.
proto/zetachain/zetacore/observer/events.proto	Added EventBallotDeleted message and imported ballot.proto.
proto/zetachain/zetacore/observer/query.proto	Modified QueryBallotByIdentifierResponse to enforce non-nullable voters field.
testutil/keeper/mocks/emissions/observer.go	Introduced ClearMaturedBallots mock function for testing.
x/emissions/abci.go	Modified DistributeObserverRewards to handle and clear matured ballots.
x/emissions/abci_test.go	Adjusted test logic for reward distribution and ballot maturity checks.
x/emissions/types/expected_keepers.go	Added ClearMaturedBallots method to ObserverKeeper interface.
x/observer/keeper/ballot.go	Added methods for deleting individual ballots and lists, and clearing matured ballots.
x/observer/keeper/ballot_test.go	Added tests for deleting ballots, clearing matured ballots, and ensuring correct behavior.
x/observer/keeper/events.go	Introduced EmitEventBallotDeleted for emitting deletion events.
x/observer/keeper/events_test.go	Created tests for EmitEventBallotDeleted functionality.
x/observer/keeper/grpc_query_ballot.go	Simplified voter list construction using GenerateVoterList method.
x/observer/keeper/grpc_query_ballot_test.go	Changed Voters field type in response struct from pointer to value slice.
x/observer/types/ballot.go	Added GenerateVoterList method to Ballot struct for generating voter lists.
x/observer/types/ballot_test.go	Added tests for GenerateVoterList method to validate voter list generation.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant Keeper
    participant EventManager

    User->>Keeper: Request to delete matured ballots
    Keeper->>Keeper: Identify matured ballots
    Keeper->>Keeper: Delete matured ballots
    Keeper->>EventManager: Emit EventBallotDeleted
    EventManager-->>Keeper: Confirmation of event emission

Assessment against linked issues

Objective	Addressed	Explanation
Delete matured ballots (##942)	✅
Add an event when the ballot gets deleted (##942)	✅

Possibly related PRs

• #2863 - Directly relates to the deletion of matured ballots, which is a core focus of this PR.
• #2861 - Enhances event handling, which may indirectly affect ballot management processes.

Suggested labels

breaking:cli, chain:solana

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.65217% with 6 lines in your changes missing coverage. Please review.

Project coverage is 62.53%. Comparing base (7eea20e) to head (950141f). Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
x/observer/keeper/grpc_query_ballot.go	73.91%	4 Missing and 2 partials :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2863      +/-   ##
===========================================
+ Coverage    62.43%   62.53%   +0.10%     
===========================================
  Files          449      450       +1     
  Lines        31706    31811     +105     
===========================================
+ Hits         19795    19894      +99     
- Misses       11024    11028       +4     
- Partials       887      889       +2     

Files with missing lines	Coverage Δ
x/emissions/abci.go	94.26% <100.00%> (+1.08%)	:arrow_up:
x/observer/keeper/ballot.go	100.00% <100.00%> (ø)
x/observer/migrations/v9/migrate.go	100.00% <100.00%> (ø)
x/observer/keeper/grpc_query_ballot.go	90.32% <73.91%> (-9.68%)	:arrow_down:

[lumtis]

Small note: let's keep this one aside for now to not introduce migration scripts as we already heavy operations with gateway and Solana

[kingpinXD]

Hi @lumtis Should we revisit this for the next release?

We can consider breaking the pr down, into

• Change in logic
• Migration script And only add the former if in case a long-running migration script is not desired

[lumtis]

Hi @lumtis Should we revisit this for the next release?

We can consider breaking the pr down, into

• Change in logic
• Migration script And only add the former if in case a long-running migration script is not desired

We actually want to remove all old ballot so we can easily query all active ballots

[lumtis]

The PR looks good to me, let's just wrap up v25 first before merging it