Added root Ghost server/API test agent

refs https://github.com/TryGhost/Team/issues/1640

- Some tests require making request to the root of the mounted server path like `GET /ghost/.well-known/jwks.json`. These are not stricly APIs like Admin, Content, and Members. They do need a separate agent to distinguish the configuration - for this agetn we can stop loading some parts like "server" in the future to speed things up (didn't work straight out of the box)

test/utils/e2e-framework.js

@@ -30,6 +30,7 @@ const boot = require('../../core/boot');
 const AdminAPITestAgent = require('./admin-api-test-agent');
 const MembersAPITestAgent = require('./members-api-test-agent');
 const ContentAPITestAgent = require('./content-api-test-agent');
+const GhostAPITestAgent = require('./ghost-api-test-agent');
 const db = require('./db-utils');
 
 // Services that need resetting
@@ -219,6 +220,32 @@ const getMembersAPIAgent = async () => {
     }
 };
 
+/**
+ * Creates a GhostAPITestAgent, which is a drop-in substitution for supertest
+ * It is automatically hooked up to the Ghost API so you can make requests to e.g.
+ * agent.get('/well-known/jwks.json') without having to worry about URL paths
+ *
+ * @returns {Promise<GhostAPITestAgent>} agent
+ */
+const getGhostAPIAgent = async () => {
+    const bootOptions = {
+        frontend: false
+    };
+
+    try {
+        const app = await startGhost(bootOptions);
+        const originURL = configUtils.config.get('url');
+
+        return new GhostAPITestAgent(app, {
+            apiURL: '/ghost/',
+            originURL
+        });
+    } catch (error) {
+        error.message = `Unable to create test agent. ${error.message}`;
+        throw error;
+    }
+};
+
 /**
  *
  * @returns {Promise<{adminAgent: AdminAPITestAgent, membersAgent: MembersAPITestAgent}>} agents
@@ -260,7 +287,8 @@ module.exports = {
         getAdminAPIAgent,
         getMembersAPIAgent,
         getContentAPIAgent,
-        getAgentsForMembers
+        getAgentsForMembers,
+        getGhostAPIAgent
     },
 
     // Mocks and Stubs

test/utils/ghost-api-test-agent.js

@@ -0,0 +1,19 @@
+const TestAgent = require('./test-agent');
+
+/**
+ * NOTE: this class is not doing much at the moment. It's rather a placeholder to test
+ * any Ghost API specific functionality, like /.well-known. If there is none in the nearest
+ * future, it would make sense to remove it alltogether.
+ * @constructor
+ * @param {Object} app  Ghost express app instance
+ * @param {Object} options
+ * @param {String} options.apiURL
+ * @param {String} options.originURL
+ */
+class GhostAPITestAgent extends TestAgent {
+    constructor(app, options) {
+        super(app, options);
+    }
+}
+
+module.exports = GhostAPITestAgent;