Added new Tier e2e test

refs https://github.com/TryGhost/Team/issues/1446

- Added a test for successfully creating a new tier.

ghost/core/test/e2e-api/admin/__snapshots__/tiers.test.js.snap

@@ -48,6 +48,30 @@ Object {
 }
 `;
 
+exports[`Tiers API Can create a new tier 1: [body] 1`] = `
+Object {
+  "tiers": Array [
+    Object {
+      "active": true,
+      "benefits": Array [],
+      "created_at": StringMatching /\\\\d\\{4\\}-\\\\d\\{2\\}-\\\\d\\{2\\}/,
+      "currency": "USD",
+      "description": null,
+      "id": StringMatching /\\[a-f0-9\\]\\{24\\}/,
+      "monthly_price": 100,
+      "name": "new premium tier",
+      "slug": "new-premium-tier",
+      "trial_days": 0,
+      "type": "paid",
+      "updated_at": null,
+      "visibility": "public",
+      "welcome_page_url": null,
+      "yearly_price": 5000,
+    },
+  ],
+}
+`;
+
 exports[`Tiers API Can edit tier properties and relations 1: [body] 1`] = `
 Object {
   "meta": Object {

ghost/core/test/e2e-api/admin/tiers.test.js

@@ -166,4 +166,27 @@ describe('Tiers API', function () {
                 })
             });
     });
+
+    it('Can create a new tier', async function () {
+        const tier = {
+            name: 'new premium tier',
+            monthly_price: 100,
+            currency: 'usd'
+        };
+
+        await agent
+            .post('/tiers/')
+            .body({tiers: [tier]})
+            .expectStatus(201)
+            .matchBodySnapshot({
+                tiers: Array(1).fill({
+                    id: matchers.anyObjectId,
+                    created_at: matchers.anyISODate,
+                    name: 'new premium tier',
+                    slug: 'new-premium-tier',
+                    monthly_price: 100,
+                    currency: 'USD'
+                })
+            });
+    });
 });