Add dummy Debug instance to authority discovery service. (#9156)

* Add dummy Debug instance to AuthorityDiscoveryService.

* Update client/authority-discovery/src/service.rs

More idiomatic print

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

substrate/client/authority-discovery/src/service.rs

@@ -16,6 +16,8 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+use std::fmt::Debug;
+
 use crate::ServicetoWorkerMsg;
 
 use futures::channel::{mpsc, oneshot};
@@ -30,6 +32,12 @@ pub struct Service {
 	to_worker: mpsc::Sender<ServicetoWorkerMsg>,
 }
 
+impl Debug for Service {
+	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+		f.debug_tuple("AuthorityDiscoveryService").finish()
+	}
+}
+
 /// A [`Service`] allows to interact with a [`crate::Worker`], e.g. by querying the
 /// [`crate::Worker`]'s local address cache for a given [`AuthorityId`].
 impl Service {