chore(samples): add auth samples (#398)

samples/authenticate_implicit_with_adc.rb

@@ -0,0 +1,47 @@
+# Copyright 2022 Google, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# [START auth_cloud_implicit_adc]
+def authenticate_implicit_with_adc project_id:
+  # The ID of your Google Cloud project
+  # project_id = "your-google-cloud-project-id"
+
+  ###
+  # When interacting with Google Cloud Client libraries, the library can auto-detect the
+  # credentials to use.
+  # TODO(Developer):
+  #   1. Before running this sample,
+  #      set up ADC as described in https://cloud.google.com/docs/authentication/external/set-up-adc
+  #   2. Replace the project variable.
+  #   3. Make sure that the user account or service account that you are using
+  #      has the required permissions. For this sample, you must have "storage.buckets.list".
+  ###
+
+  require "google/cloud/storage"
+
+  # This sample demonstrates how to list buckets.
+  # *NOTE*: Replace the client created below with the client required for your application.
+  # Note that the credentials are not specified when constructing the client.
+  # Hence, the client library will look for credentials using ADC.
+  storage = Google::Cloud::Storage.new project_id: project_id
+  buckets = storage.buckets
+  puts "Buckets: "
+  buckets.each do |bucket|
+    puts bucket.name
+  end
+  puts "Listed all storage buckets."
+end
+# [END auth_cloud_implicit_adc]
+
+authenticate_implicit_with_adc project_id: ARGV.shift if $PROGRAM_NAME == __FILE__