Enable usage of oauth2 frontend provider

packages/core-api/src/apis/definitions/auth.ts

@@ -299,7 +299,11 @@ export const microsoftAuthApiRef = createApiRef<
  * Provides authentication for custom identity providers.
  */
 export const oauth2ApiRef = createApiRef<
-  OAuthApi & OpenIdConnectApi & ProfileInfoApi & SessionStateApi
+  OAuthApi &
+    OpenIdConnectApi &
+    ProfileInfoApi &
+    SessionStateApi &
+    BackstageIdentityApi
 >({
   id: 'core.auth.oauth2',
   description: 'Example of how to use oauth2 custom provider',

packages/core-api/src/apis/implementations/auth/oauth2/OAuth2.ts

@@ -42,6 +42,7 @@ type CreateOptions = {
 
   environment?: string;
   provider?: AuthProvider & { id: string };
+  defaultScopes?: string[];
 };
 
 export type OAuth2Response = {
@@ -70,6 +71,11 @@ class OAuth2
     environment = 'development',
     provider = DEFAULT_PROVIDER,
     oauthRequestApi,
+    defaultScopes = [
+      'openid',
+      `${SCOPE_PREFIX}userinfo.email`,
+      `${SCOPE_PREFIX}userinfo.profile`,
+    ],
   }: CreateOptions) {
     const connector = new DefaultAuthConnector({
       discoveryApi,
@@ -93,11 +99,7 @@ class OAuth2
 
     const sessionManager = new RefreshingAuthSessionManager({
       connector,
-      defaultScopes: new Set([
-        'openid',
-        `${SCOPE_PREFIX}userinfo.email`,
-        `${SCOPE_PREFIX}userinfo.profile`,
-      ]),
+      defaultScopes: new Set(defaultScopes),
       sessionScopes: (session: OAuth2Session) => session.providerInfo.scopes,
       sessionShouldRefresh: (session: OAuth2Session) => {
         const expiresInSec =