History Service: Make it possible to push multiple consumer locations

[unstubbable]

To trigger a navigation from a Feature App to another page that composes a different set of Feature Apps, some kind of navigation Feature Service that encapsulates integrator routing logic would be needed.

Such a Feature Service would have the need to collect consumer locations from multiple Feature Services, and then push a root location that combines these consumer locations to the root history.

To accomplish that, the following changes to the History Service are proposed:

+export interface ConsumerLocation {
+  readonly historyKey: string;
+  readonly location: history.Location;
+}
+
+export interface RootHistory {
+  push(location: history.Location): void;
+  replace(location: history.Location): void;
+  createHref(location: history.Location): string;
+  createLocation(...consumerLocations: ConsumerLocation[]): history.Location;
+}
+
 export interface HistoryServiceV1 {
+  readonly historyKey: string;
+  readonly browserRootHistory: RootHistory;
+  readonly staticRootHistory: RootHistory;
+
+  /**
+   * @deprecated Use [[staticRootHistory.location]] instead.
+   */
   readonly staticRootLocation: history.Location;
 
   createBrowserHistory(): history.History;
   createStaticHistory(): history.History;
}

[clebert]

New Proposal as discussed with Stefan:

export interface ConsumerLocation {
  readonly historyKey: string;
  readonly location: history.Location;
}

export interface RootHistoryV2 {
  readonly location: history.Location;

  push(location: history.Location): void;
  replace(location: history.Location): void;
  createHref(location: history.Location): string;
  createLocation(...consumerLocations: ConsumerLocation[]): history.Location;
}

export interface HistoryServiceV2 {
  readonly historyKey: string;
  readonly history: history.History;
  readonly rootHistory: RootHistoryV2;
}

[clebert]

Shouldn't historyKey actually be called consumerHistoryKey?

[unstubbable]

RootHistoryV2 also needs location.