Fixed members connect endpoint returning JSON

refs: https://github.com/TryGhost/Toolbox/issues/245
refs: https://github.com/TryGhost/Team/issues/1360

- As a result of my changes in https://github.com/TryGhost/Ghost/commit/3bd4d098 the members connect endpoint had started returning JSON
- This is because the members connect endpoint relied on the old default behaviour of the serializer being to return no response, whereas now it does our default JSON response format
- I had written a tool to iterate over all endpoints and ensure that they all had explicit serializers before changing the default behaviour, but it missed this endpoint due to the snake case naming
- I have double checked and this was the only missed endpoint, the only other one was member_signin_urls.permissions but that was not a true endpoint and was removed in https://github.com/TryGhost/Ghost/commit/202696382
- Note: the snapshot file for this test was generated from running the test against https://github.com/TryGhost/Ghost/commit/e6b92aed9 - one commit before I added the new default behaviour.
  - Without the new serializer this test fails on main
  - With the new serialzier, this test passes again, showing the response format has gone back to what we expect

core/server/api/canary/utils/serializers/output/index.js

@@ -147,5 +147,9 @@ module.exports = {
 
     get offers() {
         return require('./offers');
+    },
+
+    get members_stripe_connect() {
+        return require('./members-stripe-connect');
     }
 };

core/server/api/canary/utils/serializers/output/members-stripe-connect.js

@@ -0,0 +1,6 @@
+module.exports = {
+    all() {
+        // No response
+        return;
+    }
+};

test/e2e-api/admin/__snapshots__/members-stripe-connect.test.js.snap

@@ -0,0 +1,18 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Members Stripe Connect API can do auth 1: [body] 1`] = `Object {}`;
+
+exports[`Members Stripe Connect API can do auth 2: [headers] 1`] = `
+Object {
+  "access-control-allow-origin": "http://127.0.0.1:2369",
+  "cache-control": "no-cache, private, no-store, must-revalidate, max-stale=0, post-check=0, pre-check=0",
+  "content-length": "289",
+  "content-type": "text/plain; charset=utf-8",
+  "location": StringMatching /\\^https:\\\\/\\\\/connect\\\\\\.stripe\\\\\\.com\\\\/oauth\\\\/authorize\\\\\\?response_type=code&scope=read_write&client_id=/,
+  "set-cookie": Array [
+    StringMatching /\\^ghost-admin-api-session=/,
+  ],
+  "vary": "Origin, Accept, Accept-Encoding",
+  "x-powered-by": "Express",
+}
+`;

test/e2e-api/admin/members-stripe-connect.test.js

@@ -0,0 +1,25 @@
+const {agentProvider, fixtureManager, matchers} = require('../../utils/e2e-framework');
+const {stringMatching} = matchers;
+
+describe('Members Stripe Connect API', function () {
+    let agent;
+
+    before(async function () {
+        agent = await agentProvider.getAdminAPIAgent();
+        await fixtureManager.init();
+        await agent.loginAsOwner();
+    });
+
+    it('can do auth', async function () {
+        await agent
+            .get(`members/stripe_connect`)
+            .expectStatus(302)
+            .matchBodySnapshot()
+            .matchHeaderSnapshot({
+                location: stringMatching(/^https:\/\/connect\.stripe\.com\/oauth\/authorize\?response_type=code&scope=read_write&client_id=/),
+                'set-cookie': [
+                    stringMatching(/^ghost-admin-api-session=/)
+                ]
+            });
+    });
+});