feat(samples): add sample of configuring alternate apiEndpoint (#473)

vision/samples/setEndpoint.js

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+// Copyright 2019 Google LLC
+//
+// 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
+//
+//     https://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.
+
+'use strict';
+
+async function setEndpoint() {
+  // [START vision_set_endpoint]
+  // Imports the Google Cloud client library
+  const vision = require('@google-cloud/vision');
+
+  // Specifies the location of the api endpoint
+  const clientOptions = {apiEndpoint: 'eu-vision.googleapis.com'};
+
+  // Creates a client
+  const client = new vision.ImageAnnotatorClient(clientOptions);
+  // [END vision_set_endpoint]
+
+  // Performs label detection on the image file
+  const [result] = await client.labelDetection('./resources/wakeupcat.jpg');
+  const labels = result.labelAnnotations;
+  console.log('Labels:');
+  labels.forEach(label => console.log(label.description));
+}
+
+setEndpoint().catch(console.error);

vision/samples/system-test/setEndpoint.test.js

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+// Copyright 2019 Google LLC
+//
+// 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
+//
+//     https://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.
+
+'use strict';
+
+const {assert} = require('chai');
+const cp = require('child_process');
+
+const execSync = cmd => cp.execSync(cmd, {encoding: 'utf-8'});
+
+describe(`set endpoint for vision api call`, () => {
+  it(`should detect labels in a remote file from a pre-set api endpoint`, async () => {
+    const stdout = execSync('node setEndpoint.js');
+    assert.match(stdout, /Labels:/);
+    assert.match(stdout, /cat/);
+  });
+});