Add login form extension point (#2088)

One of our users would like to create a new plugin that provides alternative methods of authentication. For that purpose, we need an additional extension point that can either replace the login form entirely, or extend it by adding login buttons. By default, the extension point simply renders the original login form.

scm-ui/ui-extensions/src/extensionPoints.ts

@@ -44,7 +44,7 @@ import {
   RepositoryTypeCollection,
   Tag,
   User,
-  ContentType
+  ContentType,
 } from "@scm-manager/ui-types";
 import { ExtensionPointDefinition } from "./binder";
 import { RenderableExtensionPointDefinition, SimpleRenderableDynamicExtensionPointDefinition } from "./ExtensionPoint";
@@ -650,3 +650,5 @@ export type FileViewActionBarOverflowMenu = ExtensionPointDefinition<
   ActionMenuProps | ModalMenuProps | LinkMenuProps,
   ContentActionExtensionProps
 >;
+
+export type LoginForm = RenderableExtensionPointDefinition<"login.form">;