Authentication of PeerIds in authority discovery records (#10317)

* Consolidating test and production code

* Signing/verifying authority discovery records with PeerId

Unsigned records cannot be rejected yet, they just produce
a warning in the log.

* Upgrading to libp2p 0.40

* libp2p::identity and sp_core::crypto Ed25519 are compatible

* Rejecting authority records unsigned by peer id can be configured

* Fixes based on review comments

* No command-line argument needed

* info was still too much spam in the logs

* Added tests for both strict and loose validation

* Fixing based on review comments

* Pierre preferred a signing method

* Ooops, I need to slow down

* Update bin/node/cli/src/service.rs

* Reexport libp2p crypto used in sc-network

* Added proto3 compatibility tests. And import noise.

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/client/keystore/src/local.rs

@@ -420,8 +420,6 @@ impl KeystoreInner {
 	/// Write the given `data` to `file`.
 	fn write_to_file(file: PathBuf, data: &str) -> Result<()> {
 		let mut file = File::create(file)?;
-		serde_json::to_writer(&file, data)?;
-		file.flush()?;
 
 		#[cfg(target_family = "unix")]
 		{
@@ -429,6 +427,8 @@ impl KeystoreInner {
 			file.set_permissions(fs::Permissions::from_mode(0o600))?;
 		}
 
+		serde_json::to_writer(&file, data)?;
+		file.flush()?;
 		Ok(())
 	}