AmplifyBackend Update: Imports an existing backend authentication resource.

Author: AWS

.changes/next-release/feature-AmplifyBackend-cb5663e.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AmplifyBackend",
+    "contributor": "",
+    "description": "Imports an existing backend authentication resource."
+}