Ipfs private swarms interop example (#1420)

* Add gossipsub and ping

* Implement swarm key parsing from environment

* WIP remove stuff

* WIP remove more stuff

* Use gossipsub instead of floodsub

* Make ipfs example work with or without swarm key

* Add support for /ipfs/Qm1234 multiaddrs

* Add documentation for ipfs example

* Rename example to ipfs-private

* Fix comments

* Move EitherTransport into either.rs

And prettify imports of ipfs-private example

* Sanitize multiaddr before parsing

...and remove the "ipfs" protocol from multiaddr

* Remove TSubstream type parameter

...so that it works with current master

* PR feedback

use source instead of cause

protocols/pnet/src/lib.rs

@@ -161,6 +161,21 @@ pub enum KeyParseError {
     InvalidKeyChar(ParseIntError),
 }
 
+impl fmt::Display for KeyParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
+impl error::Error for KeyParseError {
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        match *self {
+            KeyParseError::InvalidKeyChar(ref err) => Some(err),
+            _ => None,
+        }
+    }
+}
+
 /// Private network configuration
 #[derive(Debug, Copy, Clone)]
 pub struct PnetConfig {