Improved webhooks e2e test bootstrap speed

refs https://github.com/TryGhost/Toolbox/issues/214

- Calling `getMembersAPIAgent` and `getAdminAPIAgent` separately was booting Ghost twice, which caused a significant performance degradation.
- Additionally, having two calls was slightly ugly and having once utility function that delivers multiple agents at once feels like  more readable syntax

test/e2e-api/members/webhooks.test.js

@@ -14,8 +14,11 @@ describe('Members API', function () {
         // And it's initialised at boot - so mocking it before
         // Probably wanna replace this with a settinfs fixture mock or smth??
         mockManager.setupStripe();
-        membersAgent = await agentProvider.getMembersAPIAgent();
-        adminAgent = await agentProvider.getAdminAPIAgent();
+
+        const agents = await agentProvider.getAgentsForMembers();
+        membersAgent = agents.membersAgent;
+        adminAgent = agents.adminAgent;
+
         await fixtureManager.init('members');
         await adminAgent.loginAsOwner();
     });

test/utils/e2e-framework.js

@@ -196,11 +196,47 @@ const getMembersAPIAgent = async () => {
     }
 };
 
+/**
+ *
+ * @returns {Promise<{adminAgent: TestAgent, membersAgent: TestAgent}>} agent
+ */
+const getAgentsForMembers = async () => {
+    let membersAgent;
+    let adminAgent;
+
+    const bootOptions = {
+        frontend: true
+    };
+
+    try {
+        const app = await startGhost(bootOptions);
+        const originURL = configUtils.config.get('url');
+
+        membersAgent = new TestAgent(app, {
+            apiURL: '/members/',
+            originURL
+        });
+        adminAgent = new TestAgent(app, {
+            apiURL: '/ghost/api/canary/admin/',
+            originURL
+        });
+    } catch (error) {
+        error.message = `Unable to create test agent. ${error.message}`;
+        throw error;
+    }
+
+    return {
+        adminAgent,
+        membersAgent
+    };
+};
+
 module.exports = {
     // request agent
     agentProvider: {
         getAdminAPIAgent,
-        getMembersAPIAgent
+        getMembersAPIAgent,
+        getAgentsForMembers
     },
 
     // Mocks and Stubs