Keystore overhaul (iter 2) (#13634)

* Remove bloat about remote keystore

* Update docs and remove unused 'KeystoreRef' trait

* Use wherever possible, MemoryKeystore for testing

* Remove unrequired fully qualified method syntax for Keystore

substrate/bin/node-template/node/src/service.rs

@@ -5,7 +5,6 @@ use sc_client_api::BlockBackend;
 use sc_consensus_aura::{ImportQueueParams, SlotProportion, StartAuraParams};
 use sc_consensus_grandpa::SharedVoterState;
 pub use sc_executor::NativeElseWasmExecutor;
-use sc_keystore::LocalKeystore;
 use sc_service::{error::Error as ServiceError, Configuration, TaskManager, WarpSyncParams};
 use sc_telemetry::{Telemetry, TelemetryWorker};
 use sp_consensus_aura::sr25519::AuthorityPair as AuraPair;
@@ -58,10 +57,6 @@ pub fn new_partial(
 	>,
 	ServiceError,
 > {
-	if config.keystore_remote.is_some() {
-		return Err(ServiceError::Other("Remote Keystores are not supported.".into()))
-	}
-
 	let telemetry = config
 		.telemetry_endpoints
 		.clone()
@@ -147,13 +142,6 @@ pub fn new_partial(
 	})
 }
 
-fn remote_keystore(_url: &String) -> Result<Arc<LocalKeystore>, &'static str> {
-	// FIXME: here would the concrete keystore be built,
-	//        must return a concrete type (NOT `LocalKeystore`) that
-	//        implements `Keystore`
-	Err("Remote Keystore not supported.")
-}
-
 /// Builds a new service for a full client.
 pub fn new_full(mut config: Configuration) -> Result<TaskManager, ServiceError> {
 	let sc_service::PartialComponents {
@@ -161,22 +149,12 @@ pub fn new_full(mut config: Configuration) -> Result<TaskManager, ServiceError>
 		backend,
 		mut task_manager,
 		import_queue,
-		mut keystore_container,
+		keystore_container,
 		select_chain,
 		transaction_pool,
 		other: (block_import, grandpa_link, mut telemetry),
 	} = new_partial(&config)?;
 
-	if let Some(url) = &config.keystore_remote {
-		match remote_keystore(url) {
-			Ok(k) => keystore_container.set_remote_keystore(k),
-			Err(e) =>
-				return Err(ServiceError::Other(format!(
-					"Error hooking up remote keystore for {}: {}",
-					url, e
-				))),
-		};
-	}
 	let grandpa_protocol_name = sc_consensus_grandpa::protocol_standard_name(
 		&client.block_hash(0).ok().flatten().expect("Genesis block exists; qed"),
 		&config.chain_spec,