Tidy up stale connections. (#406)

* If messageId changes and network ID doesn't, remove 'old' message_id

* Boot nodes/connection when no recent messages received for it

* Separate task needed for soketto recv to avoid cancel-safety issues with new interval

* Wee tidy up

* cargo fmt

* Add some logging around node adding/removing

* Another log info msg

* a bit of tidy up

* bump stale node timeout to 60s

backend/Cargo.lock

@@ -31,6 +31,9 @@ name = "arrayvec"
 version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "be4dc07131ffa69b8072d35f5007352af944213cde02545e2103680baed38fcd"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "atty"
@@ -198,6 +201,7 @@ name = "common"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "arrayvec",
  "base64",
  "bimap",
  "bincode",