Introduce srml/im-online (#3079)

* Fix grammar and typo

* Extend network service

* Extend offchain API

* Support creating unsigned UncheckedExtrinsic

* Introduce srml/im-online

* Bump impl and spec version

* Fix web-wasm test

* Apply suggestions from code review

Remove parity-multiaddr dependency

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Replace transmute with from_raw_parts

* Replace PeerId.to_string() with .to_base58()

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Update Cargo.lock

* Bump impl and spec version (again)

It was updated in master in the meantime.

* Apply suggestions from code review

Co-Authored-By: Sergei Pepyakin <sergei@parity.io>

* Address comments

* Add public function is_online_in_current_session()

* Bump spec_version

* Fix doc tests

* Improve comments

* Remove superfluous line

* Name parameters consistently

* Implement comments

* Switch From to TryFrom

* Use Vec instead of HashSet

* Fix tests

* Revert me: local testing

* Fix check if already sent during session

We gossip each session, hence we need to check
if already sent in this session (not era).

* Fix typos

* Consistent terminology

* Revert "Revert me: local testing"

This reverts commit 73fbc29ff3e5ed71d99436318260b4f007e837f4.

* Introduce IsMember trait

* Implement misc comments

* Remove unused function

* Fix test

* Fix external_addresses being written

* Fix test

* Add necessary trait bound

* Do not increment version

* Update lib.rs

substrate/core/sr-io/src/lib.rs

@@ -38,6 +38,7 @@ use primitives::offchain::{
 	HttpRequestId, HttpRequestStatus, HttpError,
 	CryptoKind, CryptoKeyId,
 	StorageKind,
+	OpaqueNetworkState,
 };
 
 /// Error verifying ECDSA signature
@@ -239,6 +240,13 @@ export_api! {
 		/// The transaction will end up in the pool.
 		fn submit_transaction<T: codec::Encode>(data: &T) -> Result<(), ()>;
 
+		/// Returns information about the local node's network state.
+		fn network_state() -> Result<OpaqueNetworkState, ()>;
+
+		/// Returns the currently configured authority public key, if available.
+		// TODO [#3139] change into crypto_pubkey(&self, key: Option<CryptoKeyId>, kind: CryptoKind)
+		fn authority_pubkey(crypto: CryptoKind) -> Result<Vec<u8>, ()>;
+
 		/// Create new key(pair) for signing/encryption/decryption.
 		///
 		/// Returns an error if given crypto kind is not supported.
@@ -313,7 +321,7 @@ export_api! {
 		/// offchain worker tasks running on the same machine. It IS persisted between runs.
 		fn local_storage_get(kind: StorageKind, key: &[u8]) -> Option<Vec<u8>>;
 
-		/// Initiaties a http request given HTTP verb and the URL.
+		/// Initiates a http request given HTTP verb and the URL.
 		///
 		/// Meta is a future-reserved field containing additional, parity-codec encoded parameters.
 		/// Returns the id of newly started request.