Deprecate transition methods of controller and route

tests/dummy/app/templates/docs/deprecations.md

@@ -1,5 +1,128 @@
 # Deprecations
 
+### § Transition methods of Controller and Route
+
+**until**: 1.0.0
+
+**id**: ember-engines.transition-methods
+
+[RFC #674](https://github.com/emberjs/rfcs/pull/674) has deprecated the methods `transitionTo` and `replaceWith`
+of the `Route` and the methods `transitionToRoute` and `replaceRoute` of `Controller`.
+These methods have been removed in v5.0.0 of Ember.js, and developers encouraged to use `RouterService` instead.
+
+The methods `transitionToExternal` and `replaceWithExternal` of the `Route` and the method `transitionToExternalRoute` of the `Controller`
+share the same underlying code and follow the same spirit as ones deprecated in Ember.js.
+Developers encouraged to use `EnginesRouterService` provided by [`ember-engines-router-service`](https://github.com/villander/ember-engines-router-service) instead.
+
+Before:
+
+```js
+// my-engine/routes/foo.js
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class FooRoute extends Route {
+  @service session;
+
+  beforeModel() {
+    if (!this.session.isAuthenticated) {
+      this.transitionToExternal('login');
+    }
+  }
+}
+```
+
+After:
+
+```js
+// my-engine/routes/foo.js
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class FooRoute extends Route {
+  @service router;
+  @service session;
+
+  beforeModel() {
+    if (!this.session.isAuthenticated) {
+      this.router.transitionToExternal('login');
+    }
+  }
+}
+```
+
+Before:
+
+```js
+// my-engine/routes/foo.js
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class FooRoute extends Route {
+  @service session;
+
+  beforeModel() {
+    if (!this.session.isAuthenticated) {
+      this.replaceWithExternal('login');
+    }
+  }
+}
+```
+
+After:
+
+```js
+// my-engine/routes/foo.js
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class FooRoute extends Route {
+  @service router;
+  @service session;
+
+  beforeModel() {
+    if (!this.session.isAuthenticated) {
+      this.router.replaceWithExternal('login');
+    }
+  }
+}
+```
+
+Before:
+
+```js
+// my-engine/controllers/foo.js
+import Controller from '@ember/controller';
+
+export default class FooController extends Controller {
+  @action
+  async save({ title, text }) {
+    let post = this.store.createRecord('post', { title, text });
+    await post.save();
+    return this.transitionToExternalRoute('post', post.id);
+  }
+}
+```
+
+After:
+
+```js
+// my-engine/controllers/foo.js
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class FooRoute extends Route {
+  @service router;
+
+  @action
+  async save({ title, text }) {
+    let post = this.store.createRecord('post', { title, text });
+    await post.save();
+    return this.router.transitionToExternal('post', post.id);
+  }
+}
+```
+
 ### § Use alias for inject router service from host application
 
 **until**: 0.9.0