chore(sequencer): implement market endpoint (#1946)

## Summary
This is a small PR to address a couple of minor omissions: implementing
a query endpoint, and removing a needless RPC call.

## Background
These are likely just small omissions from previous work/discussions.

## Changes
- Updated `MarketMapQueryService::market` to not always return a "not
implemented" error response.
- Changed initial connection attempts to oracle sidecar to not actually
send a request.

## Testing
Manually tested both changes locally. The former would ideally have unit
tests, but this entire module is not unit tested. The latter is harder
to create a meaningful unit test for, but new smoke tests using the
sidecar will make it apparent if this function is broken.

## Changelogs
No updates required.

crates/astria-sequencer/src/grpc/connect.rs

@@ -101,9 +101,30 @@ impl MarketMapQueryService for SequencerServer {
     #[instrument(skip_all)]
     async fn market(
         self: Arc<Self>,
-        _request: Request<MarketRequest>,
+        request: Request<MarketRequest>,
     ) -> Result<Response<MarketResponse>, Status> {
-        Err(Status::unimplemented("market endpoint is not implemented"))
+        let snapshot = self.storage.latest_snapshot();
+        let market_map = snapshot
+            .get_market_map()
+            .await
+            .map_err(|e| Status::internal(format!("error getting market map from storage: {e:#}")))?
+            .ok_or_else(|| Status::not_found("market map not stored"))?;
+        let raw_currency_pair = request
+            .into_inner()
+            .currency_pair
+            .ok_or_else(|| Status::invalid_argument("`currency_pair` must be set"))?;
+        let currency_pair = CurrencyPair::try_from_raw(raw_currency_pair)
+            .map_err(|e| Status::invalid_argument(format!("invalid `currency_pair`: {e:#}")))?
+            .to_string();
+        let market = market_map
+            .markets
+            .get(&currency_pair)
+            .cloned()
+            .ok_or_else(|| Status::not_found(format!("`{currency_pair}` not in market map")))?;
+
+        Ok(Response::new(MarketResponse {
+            market: Some(market.into_raw()),
+        }))
     }
 
     #[instrument(skip_all)]

crates/astria-sequencer/src/sequencer.rs

@@ -5,10 +5,7 @@ use astria_core::generated::{
     connect::{
         marketmap::v2::query_server::QueryServer as MarketMapQueryServer,
         oracle::v2::query_server::QueryServer as OracleQueryServer,
-        service::v2::{
-            oracle_client::OracleClient,
-            QueryPricesRequest,
-        },
+        service::v2::oracle_client::OracleClient,
     },
 };
 use astria_eyre::{
@@ -385,16 +382,12 @@ async fn new_oracle_client(config: &Config) -> Result<Option<OracleClient<Channe
 
 #[instrument(skip_all, err(level = tracing::Level::WARN))]
 async fn connect_to_oracle(endpoint: &Endpoint, uri: &Uri) -> Result<OracleClient<Channel>> {
-    let mut oracle_client = OracleClient::new(
+    let oracle_client = OracleClient::new(
         endpoint
             .connect()
             .await
             .wrap_err("failed to connect to oracle sidecar")?,
     );
-    let _ = oracle_client
-        .prices(QueryPricesRequest::default())
-        .await
-        .wrap_err("oracle sidecar responded with error to query for prices");
     debug!(uri = %uri, "oracle sidecar is reachable");
     Ok(oracle_client)
 }