*: Refactor authority discovery (key mngmt, runtime API) (#3955)

* {core,srml}/authority-discovery: Move generic to specific session keys

* {srml,core}/authority-discovery: Verify signature outside of runtime

Given that the `core/authority-discovery` uses concrete authority
identifiers and signatures, one can verify a signature with the
authority discovery within `core`. Given the above, the `verify` runtime
api is obsolete and thus removed.

* *: Add authority discovery to the set of session keys

* *: Sign authority discovery DHT payload with keystore instead of runtime

Instead of calling a runtime function to sign a dht payload, which then
invokes the keystore, pass the keystore to the authority discovery
module and use it directly.

* core/authority-discovery: Give libp2p Kademlia time to start up

* core/authority-discovery: Move authorities priority group name to const

* node/runtime/src/lib.rs: Bump runtime spec version

* *: Fix lints and node/testing test failures

* *: Fix formatting

* core/authority-discovery: Box dht event channel in unit tests

* node/cli/src/service.rs: Fix future import

* node/cli/src/service.rs: Replace unwrap by expect with proof

* node/cli/src/chain_spec: Remove TODO for testnet key generation

* core/authority-discovery/src/lib: Remove scale encoding TODOs

* srml/authority-discovery: Make comment a doc comment

* core/authority-discovery: Remove unused StreamExt import

* node/runtime: Bump impl version to debug CI

* Test ci.

* Change the line width to 100.

* Revert "Change the line width to 100."

This reverts commit edff1f855bc71e0418bf3a967f81a35591d882e3.

* Fix a check for polkadot to work on forked repos.

* Revert "node/runtime: Bump impl version to debug CI"

This reverts commit 1a90903b4c929bc55a9e0a538af34b50b7f65139.

* Revert "Test ci."

This reverts commit a2c9df574e645158f77cd2b3d4d9355bcae33aab.

* Cargo.lock: Fix wrong lock file merge

* srml/authority-discovery: Keep track of new validator set not upcoming

* core/authority-discovery: Document key retrieval functions

substrate/node/runtime/Cargo.toml

@@ -14,6 +14,7 @@ rustc-hex = { version = "2.0", optional = true }
 serde = { version = "1.0.102", optional = true }
 
 # primitives
+authority-discovery-primitives = { package = "substrate-authority-discovery-primitives", path = "../../core/authority-discovery/primitives", default-features = false }
 babe-primitives = { package = "substrate-consensus-babe-primitives", path = "../../core/consensus/babe/primitives", default-features = false }
 node-primitives = { path = "../primitives", default-features = false }
 offchain-primitives = { package = "substrate-offchain-primitives", path = "../../core/offchain/primitives", default-features = false }
@@ -44,6 +45,7 @@ executive = { package = "srml-executive", path = "../../srml/executive", default
 finality-tracker = { package = "srml-finality-tracker", path = "../../srml/finality-tracker", default-features = false }
 grandpa = { package = "srml-grandpa", path = "../../srml/grandpa", default-features = false }
 im-online = { package = "srml-im-online", path = "../../srml/im-online", default-features = false }
+authority-discovery = { package = "srml-authority-discovery", path = "../../srml/authority-discovery", default-features = false }
 indices = { package = "srml-indices", path = "../../srml/indices", default-features = false }
 membership = { package = "srml-membership", path = "../../srml/membership", default-features = false }
 nicks = { package = "srml-nicks", path = "../../srml/nicks", default-features = false }
@@ -71,6 +73,8 @@ runtime_io = { package = "sr-io", path = "../../core/sr-io" }
 [features]
 default = ["std"]
 std = [
+	"authority-discovery/std",
+	"authority-discovery-primitives/std",
 	"authorship/std",
 	"babe-primitives/std",
 	"babe/std",

substrate/node/runtime/src/lib.rs

@@ -42,6 +42,7 @@ use primitives::OpaqueMetadata;
 use grandpa::AuthorityList as GrandpaAuthorityList;
 use grandpa::fg_primitives;
 use im_online::sr25519::{AuthorityId as ImOnlineId};
+use authority_discovery_primitives::AuthorityId as AuthorityDiscoveryId;
 use transaction_payment_rpc_runtime_api::RuntimeDispatchInfo;
 use contracts_rpc_runtime_api::ContractExecResult;
 use system::offchain::TransactionSubmitter;
@@ -76,8 +77,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to equal spec_version. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 193,
-	impl_version: 193,
+	spec_version: 194,
+	impl_version: 194,
 	apis: RUNTIME_API_VERSIONS,
 };
 
@@ -209,6 +210,7 @@ impl_opaque_keys! {
 		pub grandpa: Grandpa,
 		pub babe: Babe,
 		pub im_online: ImOnline,
+		pub authority_discovery: AuthorityDiscovery,
 	}
 }
 
@@ -433,6 +435,8 @@ impl offences::Trait for Runtime {
 	type OnOffenceHandler = Staking;
 }
 
+impl authority_discovery::Trait for Runtime {}
+
 impl grandpa::Trait for Runtime {
 	type Event = Event;
 }
@@ -521,6 +525,7 @@ construct_runtime!(
 		Contracts: contracts,
 		Sudo: sudo,
 		ImOnline: im_online::{Module, Call, Storage, Event<T>, ValidateUnsigned, Config<T>},
+		AuthorityDiscovery: authority_discovery::{Module, Call, Config},
 		Offences: offences::{Module, Call, Storage, Event},
 		RandomnessCollectiveFlip: randomness_collective_flip::{Module, Call, Storage},
 		Nicks: nicks::{Module, Call, Storage, Event<T>},
@@ -635,6 +640,12 @@ impl_runtime_apis! {
 		}
 	}
 
+	impl authority_discovery_primitives::AuthorityDiscoveryApi<Block> for Runtime {
+		fn authorities() -> Vec<AuthorityDiscoveryId> {
+			AuthorityDiscovery::authorities()
+		}
+	}
+
 	impl system_rpc_runtime_api::AccountNonceApi<Block, AccountId, Index> for Runtime {
 		fn account_nonce(account: AccountId) -> Index {
 			System::account_nonce(account)