chore: starting to addthje scaffolder form extension point

Signed-off-by: blam <ben@blam.sh>

packages/core-api/src/extensions/extensions.tsx

@@ -20,7 +20,7 @@ import { BackstagePlugin, Extension } from '../plugin/types';
 import { RouteRef, useRouteRef } from '../routing';
 import { attachComponentData } from './componentData';
 
-type ComponentLoader<T> =
+export type ComponentLoader<T> =
   | {
       lazy: () => Promise<T>;
     }

packages/core-api/src/extensions/index.ts

@@ -20,3 +20,4 @@ export {
   createRoutableExtension,
   createComponentExtension,
 } from './extensions';
+export type { ComponentLoader } from './extensions';

plugins/scaffolder/src/extensions/index.tsx

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2021 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Extension, ComponentLoader } from '@backstage/core';
+
+export type FormExtensionOptions<T> = {
+  name: string;
+  component: ComponentLoader<T>;
+};
+
+export function createScaffolderFormExtension<
+  T extends (props: any) => JSX.Element | null
+>(options: FormExtensionOptions<T>): Extension<T> {}