feat(lib): enable overriding of the elements registry, fixes #9

- use LAZY_ELEMENTS_REGISTRY token (with LazyElementsRegistry interface)
- can be used to share registry between multiple apps / elements
- can prevent multiple downloads of the same javascript bundles

projects/elements/src/lib/lazy-elements/lazy-elements-loader.service.ts

@@ -1,7 +1,11 @@
 import { Injectable, Type, Optional, Inject } from '@angular/core';
 
 import { LazyElementRootOptions } from './lazy-elements.module';
-import { LAZY_ELEMENT_ROOT_OPTIONS } from './lazy-elements.tokens';
+import {
+  LAZY_ELEMENT_ROOT_OPTIONS,
+  LAZY_ELEMENTS_REGISTRY,
+  LazyElementsRegistry
+} from './lazy-elements.tokens';
 
 const LOG_PREFIX = '@angular-extensions/elements';
 
@@ -18,10 +22,10 @@ export interface ElementConfig {
   providedIn: 'root'
 })
 export class LazyElementsLoaderService {
-  registry: Map<string, Promise<void>> = new Map<string, Promise<void>>();
   configs: ElementConfig[] = [];
 
   constructor(
+    @Inject(LAZY_ELEMENTS_REGISTRY) private registry: LazyElementsRegistry,
     @Optional()
     @Inject(LAZY_ELEMENT_ROOT_OPTIONS)
     public options: LazyElementRootOptions

projects/elements/src/lib/lazy-elements/lazy-elements.tokens.ts

@@ -14,3 +14,17 @@ export const LAZY_ELEMENT_ROOT_OPTIONS = new InjectionToken<
 export const LAZY_ELEMENT_ROOT_GUARD = new InjectionToken<void>(
   'LAZY_ELEMENT_ROOT_GUARD'
 );
+
+export const LAZY_ELEMENTS_REGISTRY = new InjectionToken<LazyElementsRegistry>(
+  'Lazu elements registry',
+  {
+    providedIn: 'root',
+    factory: () => new Map<string, Promise<void>>()
+  }
+);
+
+export interface LazyElementsRegistry {
+  get: (url: string) => Promise<void>;
+  set: (url: string, notifier: Promise<void>) => void;
+  has: (url: string) => boolean;
+}