simplify websocket opening and response types from BE

client/lib/source/mock-source.ts

@@ -1,13 +1,11 @@
 import { Observable } from 'rxjs'
-import { map } from 'rxjs/operators'
 import { Update } from '../types'
 import { Source } from './source'
-import { RPCResponse } from './ws-source'
 
 export class MockSource<T> implements Source<T> {
   constructor(private readonly seed: Observable<Update<T>>) {}
 
-  watch$(): Observable<RPCResponse<Update<T>>> {
-    return this.seed.pipe(map(result => ({ result, jsonrpc: '2.0' })))
+  watch$(): Observable<Update<T>> {
+    return this.seed
   }
 }