client: Add new controller script to load 3rd party scripts

Add `client/external.js` which load third-party scripts passed into the
`externalLibs` array of the client config object.

client/controller/external.js

+// Load third-parties libraries given in config
+
+/* global robotController document */
+
+robotController.external = {
+  load: config => {
+    for (const url of config.externalLibs) {
+      const script = document.createElement('script');
+      script.setAttribute('type', 'text/javascript');
+      script.setAttribute('src', url);
+      document.head.appendChild(script);
+    }
+  }
+};

client/controller/external.test.js

+'use strict';
+
+/* global Object document */
+
+Object.defineProperty(document, 'appendedElements', {
+  value: []
+});
+
+Object.defineProperty(document, 'createElement', {
+  value: type => {
+    const res = {
+      type,
+      setAttribute: (k, v) => {
+        res[k] = v;
+      }
+    };
+    return res;
+  }
+});
+
+Object.defineProperty(document, 'head', {
+  value: {
+    appendChild: e => {
+      document.appendedElements.push(e);
+    }
+  }
+});
+
+describe('client/controller/external', () => {
+  beforeEach(() => {
+    global.robotController = {};
+
+    /* eslint-disable import/no-unassigned-import */
+    require('./external.js');
+    /* eslint-enable */
+  });
+
+  afterEach(() => {
+    jest.resetModules();
+  });
+
+  test('should add itself to controller', () => {
+    expect(global.robotController.external).toBeDefined();
+  });
+
+  test('should load external libs in config', () => {
+    global.robotController.external.load({
+      externalLibs: ['dep1', 'dep2', 'dep3']
+    });
+    console.log(document);
+    expect(document.appendedElements).toHaveLength(3);
+    expect(document.appendedElements[0]).toEqual(expect.objectContaining({
+      type: 'text/javascript',
+      src: 'dep1'
+    }));
+    expect(document.appendedElements[1]).toEqual(expect.objectContaining({
+      type: 'text/javascript',
+      src: 'dep2'
+    }));
+    expect(document.appendedElements[2]).toEqual(expect.objectContaining({
+      type: 'text/javascript',
+      src: 'dep3'
+    }));
+  });
+});

config.json

@@ -18,6 +18,7 @@
   },
   "client": {
     "name": "hublot",
-    "gstreamerURL": "ws://localhost:8888"
+    "gstreamerURL": "ws://localhost:8888",
+    "externalLibs": []
   }
 }