feat(btc-server): add GetPublicKeyById gRPC for multi-key support

[DariusParvin]

Issue being fixed or feature implemented

What was done?

How Has This Been Tested?

Breaking Changes

Checklist

• I have added or updated relevant unit/integration/functional/e2e tests
• I have tested my changes running a local network, and they work as expected
• I have performed a self-review
• I have commented my code, particularly in hard-to-understand areas
• I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed
• I have added assignees and reviewers to this pull request
• I have added the PR to the project board or linked it to an issue from the board

Summary by CodeRabbit

• New Features

  • Added a new RPC endpoint to retrieve public keys by multisig ID. The endpoint returns the requested public key in hex format along with the corresponding ID.

• Tests

  • Added test coverage for the new public key retrieval functionality.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

A new RPC endpoint GetPublicKeyById is added to the BtcServer service, enabling clients to retrieve hex-encoded public keys by multisig ID. The implementation introduces a shared helper function for key loading and refactors the existing legacy key retrieval to use it.

Changes

Cohort / File(s)	Summary
Protobuf Definitions bin/btc-server/proto/btc_server.proto	Added new RPC method GetPublicKeyById to BtcServer service with corresponding request/response message types: GetPublicKeyByIdRequest (multisig_id: uint32) and GetPublicKeyByIdResponse (publickey: string, multisig_id: uint32).
Generated Client Code bin/btc-server/client/src/btc_server.rs	Generated client request/response message structs and added async client method get_public_key_by_id with proper gRPC method wiring and readiness checks.
Generated Server Code bin/btc-server/src/rpc/btc_server.rs	Generated server trait method get_public_key_by_id and service routing for the new RPC endpoint, including UnaryService handler and dispatch wiring.
Server Implementation bin/btc-server/src/bin/main.rs	Added private helper load_public_key(multisig_id) to load and serialize public keys, refactored existing get_public_key to use the helper, and implemented new public RPC handler get_public_key_by_id. Includes unit test for new endpoint.

Sequence Diagram

sequenceDiagram
    participant Client
    participant BtcServerClient
    participant BtcServer
    participant App
    participant Database

    Client->>BtcServerClient: get_public_key_by_id(multisig_id)
    BtcServerClient->>BtcServer: tonic::Request<GetPublicKeyByIdRequest>
    BtcServer->>App: get_public_key_by_id(req)
    App->>Database: fetch public key package by multisig_id
    Database-->>App: public key package
    App->>App: serialize to hex string
    App-->>BtcServer: GetPublicKeyByIdResponse (publickey, multisig_id)
    BtcServer-->>BtcServerClient: tonic::Response<GetPublicKeyByIdResponse>
    BtcServerClient-->>Client: (publickey, multisig_id)

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Key areas requiring attention:
  • Verify that load_public_key correctly handles error cases and matches expected database behavior (get_public_key_package_by_id)
  • Confirm the refactoring of existing get_public_key to use the new helper maintains backward compatibility and returns identical results
  • Validate the unit test coverage for the new endpoint and edge cases (e.g., invalid multisig_id)
  • Review consistency between protobuf field tags and generated message struct definitions

Possibly related PRs

• Macbeth #1029: Introduces multi-key database APIs (get_public_key_package_by_id, LEGACY_MULTISIG_ID, migration) that this PR depends on for the load_public_key implementation

Suggested reviewers

• lamafab
• scottmillner
• rwlockbg

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 23.08% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(btc-server): add GetPublicKeyById gRPC for multi-key support' clearly and specifically describes the main change: adding a new gRPC endpoint for multi-key functionality.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/multi-key-endpoints

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

bin/btc-server/src/bin/main.rs (1)

1879-1898: Public key handlers correctly share logic and preserve legacy behavior

get_public_key now delegates to load_public_key(LEGACY_MULTISIG_ID) and get_public_key_by_id simply threads through the requested id, which keeps error behavior consistent and avoids duplication. You might optionally add a small test that get_public_key_by_id with a non‑existent multisig_id returns the expected InvalidArgument/Missing key package error, mirroring the existing get_public_key negative test.

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 5992b8c and 654440b.

📒 Files selected for processing (4)

• bin/btc-server/client/src/btc_server.rs (2 hunks)
• bin/btc-server/proto/btc_server.proto (2 hunks)
• bin/btc-server/src/bin/main.rs (4 hunks)
• bin/btc-server/src/rpc/btc_server.rs (3 hunks)

🧰 Additional context used

🧬 Code graph analysis (2)

bin/btc-server/client/src/btc_server.rs (2)

bin/btc-server/src/bin/main.rs (4)

• get_public_key_by_id (1889-1898)
• req (788-817)
• req (1080-1090)
• new (351-560)

bin/btc-server/src/rpc/btc_server.rs (2)

• get_public_key_by_id (393-399)
• new (520-522)

bin/btc-server/src/rpc/btc_server.rs (2)

bin/btc-server/client/src/btc_server.rs (2)

• get_public_key_by_id (551-574)
• new (372-375)

bin/btc-server/src/bin/main.rs (4)

• get_public_key_by_id (1889-1898)
• new (351-560)
• req (788-817)
• req (1080-1090)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: Build

🔇 Additional comments (5)

bin/btc-server/proto/btc_server.proto (1)

20-21: Proto definition for GetPublicKeyById is consistent and well-scoped

RPC signature and request/response messages line up cleanly with existing GetPublicKey and the Rust types used downstream (u32 id, hex-encoded key). No issues from a schema or compatibility standpoint.

Also applies to: 185-193

bin/btc-server/client/src/btc_server.rs (1)

159-171: Client wiring for GetPublicKeyById matches proto and existing patterns

The new request/response types and get_public_key_by_id client method follow the established tonic/prost pattern and use the correct service path. Nothing to change here.

Also applies to: 551-574

bin/btc-server/src/bin/main.rs (2)

26-26: Centralized load_public_key helper is good; confirm DB multi-key migration semantics

The load_public_key helper cleanly encapsulates lookup-by-id plus hex serialization and reuses the existing ToStatus flow and badarg!("Missing key package") semantics. The only thing to double‑check is that the DB layer guarantees get_public_key_package_by_id(LEGACY_MULTISIG_ID) is populated whenever DKG completes (e.g., via set_pubkey_package and/or migrate_legacy_key_package), so legacy flows still see the aggregated key via the new helper.

Also applies to: 676-685

---

2657-2677: New test_get_public_key_by_id_success accurately exercises the happy path

The test seeds a pubkey package under a specific multisig_id and verifies both the id echo and the hex‑encoded key match the stored package, which is exactly what this endpoint promises.

bin/btc-server/src/rpc/btc_server.rs (1)

159-171: Server-side GetPublicKeyById wiring is consistent with existing RPCs

The new messages, trait method, and /btc_server.BtcServer/GetPublicKeyById route follow the established tonic server patterns and match the proto/client definitions; no issues spotted.

Also applies to: 393-399, 809-854