feat(discovery-service): add outgoing state sync endpoint

[m-kus]

Add outgoing channel sync endpoint to discovery service

TL;DR

Implements the outgoing channel sync endpoint for the discovery service, allowing clients to discover all outgoing channels and subchannels for a sender.

What changed?

• Added the /v1/sync/outgoing_state endpoint implementation in the discovery service
• Updated the API specification in .claude/specs/discovery-service/06-api-design.md with detailed documentation for the endpoint
• Added request/response types and validation logic for the new endpoint
• Implemented integration tests for the outgoing sync endpoint

---

This change is 

[m-kus]

• feat(e2e): starknet integration demo explorer #467 : 3 dependent PRs (#480 , #502 , #512 )
• feat(discovery-service): add fallback for chain state, e2e test in the starknet integration environment #466
• feat(e2e): add indexer e2e test suite with sdk devnet helpers #486
• feat(sdk): add indexer discovery provider #485
• feat(discovery-service): add preflight check endpoint #484
• feat(discovery-service): add outgoing state sync endpoint #483 👈 (View in Graphite)
• feat(discovery-service): add incoming sync endpoint with validation and error handling #482
• feat(discovery-service): centralize configuration into config module #481
• feat(discovery-core): add transfer preflight check #474
• feat(discovery-core): add outgoing state sync orchestrator #473
• feat(discovery-core): add incoming state sync orchestrator #472
• feat(discovery-core): add paginated last-note-index search with bisection #471
• feat(discovery-core): add paginated outgoing channel discovery #470
• refactor: propagate compliance-to-auditor rename and fee params to sdk and rust #505
• main

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[Yoni-Starkware]

@Yoni-Starkware reviewed 2 files and all commit messages, and made 2 comments.
Reviewable status: 2 of 8 files reviewed, 2 unresolved discussions (waiting on m-kus).

---

crates/discovery-service/src/api/handlers.rs line 200 at r2 (raw file):

        block = %block_ref,
        "outgoing_sync request"
    );

Please share with the incoming_sync code

Code quote:

    validate_cursor(&request.cursor, &state.validation_limits)?;
    if let Some(ref recipients) = request.recipients {
        validate_recipients(recipients, &state.validation_limits)?;
    }
    let block_ref =
        validate_block_ref(request.last_known_block, request.block_ref, &state.backend).await?;
    let viewing_key = SecretFelt::new(request.viewing_key);

    let snapshot = state
        .backend
        .snapshot(request.contract_address, Some(BlockId::Hash(block_ref)))
        .await
        .map_err(|e| {
            warn!("Failed to create snapshot: {}", e);
            (
                StatusCode::INTERNAL_SERVER_ERROR,
                ApiErrorResponse::new(
                    error_codes::INTERNAL_ERROR,
                    format!("Failed to create snapshot: {}", e),
                ),
            )
        })?;

    let budget = IoBudget::new(state.validation_limits.server_budget);
    let cursor_limits = CursorLimits {
        max_channels: state.validation_limits.max_cursor_channels,
        max_subchannels: state.validation_limits.max_cursor_subchannels_per_channel,
    };

    debug!(
        sender = felt_hex(&request.sender_address),
        recipients = ?request.recipients.as_ref().map(|r| r.len()),
        block = %block_ref,
        "outgoing_sync request"
    );

---

crates/discovery-service/src/api/types.rs line 212 at r2 (raw file):

    /// response to continue discovery.
    #[serde(default)]
    pub cursor: DiscoveryCursor,

Please share with the incoming struct

Code quote:

pub struct OutgoingSyncRequest {
    /// The privacy pool contract address.
    pub contract_address: Felt,
    /// The sender's address.
    pub sender_address: Felt,
    /// The sender's private viewing key.
    pub viewing_key: Felt,
    /// Block hash for reorg detection. Set on first request of a new sync
    /// session to the `block_hash` from your last completed sync.
    /// Server returns 409 if this block was reorged out.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub last_known_block: Option<Felt>,
    /// Block hash to query state at. Ensures consistent reads across
    /// paginated requests. Leave empty on first request (server uses
    /// current head). On pagination, use the value from previous response.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub block_ref: Option<Felt>,
    /// Discovery cursor for pagination. Use the cursor from previous
    /// response to continue discovery.
    #[serde(default)]
    pub cursor: DiscoveryCursor,

[Yoni-Starkware]

@Yoni-Starkware made 1 comment.
Reviewable status: 2 of 8 files reviewed, 3 unresolved discussions (waiting on m-kus).

---

crates/discovery-service/tests/common/indexer.rs line 185 at r2 (raw file):

        let resp = reqwest::Client::new().post(&url).json(req).send().await?;

        let status = resp.status();

Please share

Code quote:

        let url = format!("http://{}/v1/sync/outgoing_state", self.api_host);
        let resp = reqwest::Client::new().post(&url).json(req).send().await?;

        let status = resp.status();

[m-kus]

@m-kus resolved 3 discussions.
Reviewable status: 2 of 8 files reviewed, all discussions resolved (waiting on Yoni-Starkware).

[Yoni-Starkware]

@Yoni-Starkware reviewed 6 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on m-kus).