enable appengineflex service to fix app engine flex version tests

.changelog/3286.txt

@@ -0,0 +1,3 @@
+```release-note:none
+
+```

google-beta/resource_app_engine_flexible_app_version_generated_test.go

@@ -28,7 +28,6 @@ func TestAccAppEngineFlexibleAppVersion_appEngineFlexibleAppVersionExample(t *te
 	t.Parallel()
 
 	context := map[string]interface{}{
-		"org_id":        getTestOrgFromEnv(t),
 		"random_suffix": acctest.RandString(10),
 	}
 
@@ -52,6 +51,12 @@ func TestAccAppEngineFlexibleAppVersion_appEngineFlexibleAppVersionExample(t *te
 
 func testAccAppEngineFlexibleAppVersion_appEngineFlexibleAppVersionExample(context map[string]interface{}) string {
 	return Nprintf(`
+resource "google_project_service" "service" {
+  service = "appengineflex.googleapis.com"
+
+  disable_dependent_services = false
+}
+
 resource "google_app_engine_flexible_app_version" "myapp_v1" {
   version_id = "v1"
   service    = "tf-test-service-%{random_suffix}"

google-beta/resource_app_engine_flexible_app_version_test.go

@@ -37,11 +37,16 @@ func TestAccAppEngineFlexibleAppVersion_update(t *testing.T) {
 			},
 		},
 	})
-
 }
 
 func testAccAppEngineFlexibleAppVersion_python(resourceName string) string {
 	return fmt.Sprintf(`
+resource "google_project_service" "project" {
+  service = "appengineflex.googleapis.com"
+
+  disable_dependent_services = false
+}
+
 resource "google_app_engine_flexible_app_version" "foo" {
   version_id = "v1"
   service    = "%s"
@@ -127,6 +132,12 @@ resource "google_storage_bucket_object" "main" {
 
 func testAccAppEngineFlexibleAppVersion_pythonUpdate(resourceName string) string {
 	return fmt.Sprintf(`
+resource "google_project_service" "project" {
+  service = "appengineflex.googleapis.com"
+
+  disable_dependent_services = false
+}
+
 resource "google_app_engine_flexible_app_version" "foo" {
   version_id = "v1"
   service    = "%s"

website/docs/r/app_engine_flexible_app_version.html.markdown

@@ -27,6 +27,9 @@ the App Engine flexible environment automatically scales your app up and down wh
 Learn about the differences between the standard environment and the flexible environment
 at https://cloud.google.com/appengine/docs/the-appengine-environments.
 
+~> **Note:** The App Engine flexible environment service account uses the member ID `service-[YOUR_PROJECT_NUMBER]@gae-api-prod.google.com.iam.gserviceaccount.com`
+It should have the App Engine Flexible Environment Service Agent role, which will be applied when the `appengineflex.googleapis.com` service is enabled.
+
 
 To get more information about FlexibleAppVersion, see:
 
@@ -43,6 +46,12 @@ To get more information about FlexibleAppVersion, see:
 
 
 ```hcl
+resource "google_project_service" "service" {
+  service = "appengineflex.googleapis.com"
+
+  disable_dependent_services = false
+}
+
 resource "google_app_engine_flexible_app_version" "myapp_v1" {
   version_id = "v1"
   service    = "service-"