refactor(router): Provide easily patchable file for assigning relativeLinkResolution (#47136)

For context on the migration plan, see b/241955063

PR Close #47136

packages/router/src/patchable_relative_link_resolution.ts

@@ -0,0 +1,13 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+/**
+ * Exists to aid internal migration off of the deprecated relativeLinkResolution option.
+ */
+export function assignRelativeLinkResolution(
+    router: {relativeLinkResolution: 'legacy'|'corrected'}): void {}

packages/router/src/router.ts

@@ -24,6 +24,7 @@ import {recognize} from './operators/recognize';
 import {resolveData} from './operators/resolve_data';
 import {switchTap} from './operators/switch_tap';
 import {DefaultTitleStrategy, TitleStrategy} from './page_title_strategy';
+import {assignRelativeLinkResolution} from './patchable_relative_link_resolution';
 import {DefaultRouteReuseStrategy, RouteReuseStrategy} from './route_reuse_strategy';
 import {ErrorHandler, ExtraOptions, ROUTER_CONFIGURATION} from './router_config';
 import {RouterConfigLoader, ROUTES} from './router_config_loader';
@@ -349,6 +350,8 @@ export function setupRouter() {
 
   assignExtraOptionsToRouter(opts, router);
 
+  assignRelativeLinkResolution(router);
+
   return router;
 }