Add error handling in case UAA is unavailable

Author: svkrieger

app/controllers/v3/users_controller.rb

@@ -45,6 +45,8 @@ def create
     user = UserCreate.new.create(message:)
 
     render status: :created, json: Presenters::V3::UserPresenter.new(user, uaa_users: User.uaa_users_info([user.guid]))
+  rescue VCAP::CloudController::UaaUnavailable
+    raise CloudController::Errors::ApiError.new_from_details('UaaUnavailable')
   rescue UserCreate::Error => e
     unprocessable!(e)
   end

lib/cloud_controller/uaa/uaa_client.rb

@@ -98,6 +98,9 @@ def origins_for_username(username)
 
     def create_shadow_user(username, origin)
       with_cache_retry { scim.add(:user, { username: username, origin: origin, emails: [{ primary: true, value: username}]}) }
+    rescue CF::UAA::BadTarget => e
+      logger.error("UAA request for creating a user failed: #{e.inspect}")
+      raise UaaUnavailable
     end
 
     def info