Pass online/offline status indicators with staking accounts (#1265)

* staking online status

* restrict onlineStatus.online to validators

* get onlineStatus for stash/validator only

* tests

* fixes

* Add offline

* Revert stash, change to stashId, linting

* Heartbeat signature

* Make CodeClimate (slightly) happier

* keep compatibility

* change status type

* rv null possible

* cleanup

packages/api-derive/src/index.ts

@@ -13,6 +13,7 @@ import * as chain from './chain';
 import * as contracts from './contracts';
 import * as democracy from './democracy';
 import * as elections from './elections';
+import * as imOnline from './imOnline';
 import * as session from './session';
 import * as staking from './staking';
 
@@ -56,7 +57,7 @@ function injectFunctions<AllSections> (api: ApiInterfaceRx, allSections: AllSect
     }, {} as unknown as DeriveSections<AllSections>);
 }
 
-export const derive = { accounts, balances, chain, contracts, democracy, elections, session, staking };
+export const derive = { accounts, balances, chain, contracts, democracy, elections, imOnline, session, staking };
 export type Derive = typeof derive;
 
 // FIXME I have no idea how to get this done