Added LightClientBootstrap V1 (#3711)

## Issue Addressed

Partially addresses #3651

## Proposed Changes

Adds server-side support for light_client_bootstrap_v1 topic

## Additional Info

This PR, creates each time a bootstrap without using cache, I do not know how necessary a cache is in this case as this topic is not supposed to be called frequently and IMHO we can just prevent abuse by using the limiter, but let me know what you think or if there is any caveat to this, or if it is necessary only for the sake of good practice.


Co-authored-by: Pawan Dhananjay <pawandhananjay@gmail.com>

beacon_node/lighthouse_network/src/rpc/outbound.rs

@@ -38,6 +38,7 @@ pub enum OutboundRequest<TSpec: EthSpec> {
     Goodbye(GoodbyeReason),
     BlocksByRange(OldBlocksByRangeRequest),
     BlocksByRoot(BlocksByRootRequest),
+    LightClientBootstrap(LightClientBootstrapRequest),
     Ping(Ping),
     MetaData(PhantomData<TSpec>),
 }
@@ -84,9 +85,12 @@ impl<TSpec: EthSpec> OutboundRequest<TSpec> {
                 ProtocolId::new(Protocol::MetaData, Version::V2, Encoding::SSZSnappy),
                 ProtocolId::new(Protocol::MetaData, Version::V1, Encoding::SSZSnappy),
             ],
+            // Note: This match arm is technically unreachable as we only respond to light client requests
+            // that we generate from the beacon state.
+            // We do not make light client rpc requests from the beacon node
+            OutboundRequest::LightClientBootstrap(_) => vec![],
         }
     }
-
     /* These functions are used in the handler for stream management */
 
     /// Number of responses expected for this request.
@@ -98,6 +102,7 @@ impl<TSpec: EthSpec> OutboundRequest<TSpec> {
             OutboundRequest::BlocksByRoot(req) => req.block_roots.len() as u64,
             OutboundRequest::Ping(_) => 1,
             OutboundRequest::MetaData(_) => 1,
+            OutboundRequest::LightClientBootstrap(_) => 1,
         }
     }
 
@@ -110,6 +115,7 @@ impl<TSpec: EthSpec> OutboundRequest<TSpec> {
             OutboundRequest::BlocksByRoot(_) => Protocol::BlocksByRoot,
             OutboundRequest::Ping(_) => Protocol::Ping,
             OutboundRequest::MetaData(_) => Protocol::MetaData,
+            OutboundRequest::LightClientBootstrap(_) => Protocol::LightClientBootstrap,
         }
     }
 
@@ -121,6 +127,7 @@ impl<TSpec: EthSpec> OutboundRequest<TSpec> {
             // variants that have `multiple_responses()` can have values.
             OutboundRequest::BlocksByRange(_) => ResponseTermination::BlocksByRange,
             OutboundRequest::BlocksByRoot(_) => ResponseTermination::BlocksByRoot,
+            OutboundRequest::LightClientBootstrap(_) => unreachable!(),
             OutboundRequest::Status(_) => unreachable!(),
             OutboundRequest::Goodbye(_) => unreachable!(),
             OutboundRequest::Ping(_) => unreachable!(),
@@ -178,6 +185,9 @@ impl<TSpec: EthSpec> std::fmt::Display for OutboundRequest<TSpec> {
             OutboundRequest::BlocksByRoot(req) => write!(f, "Blocks by root: {:?}", req),
             OutboundRequest::Ping(ping) => write!(f, "Ping: {}", ping.data),
             OutboundRequest::MetaData(_) => write!(f, "MetaData request"),
+            OutboundRequest::LightClientBootstrap(bootstrap) => {
+                write!(f, "Lightclient Bootstrap: {}", bootstrap.root)
+            }
         }
     }
 }