Fixed upgrade modal not showing when theme uploads are not allowed

closes https://github.com/TryGhost/Team/issues/1193

- there was a typo in the limits modal component name that is shown when the limits service check fails when opening the upload theme modal
- added acceptance test with associated fix of modal name test selector in the template

app/components/modals/limits/custom-theme.hbs

@@ -1,6 +1,6 @@
 
-<div class="modal-content">
-    <header class="modal-header" data-test-modal="delete-user">
+<div class="modal-content" data-test-modal="limits/custom-theme">
+    <header class="modal-header">
         <h1>Upgrade to enable custom themes</h1>
     </header>
     <button class="close" title="Close" {{on "click" @close}}>{{svg-jar "close"}}<span class="hidden">Close</span></button>

app/services/theme-management.js

@@ -52,7 +52,7 @@ export default class ThemeManagementService extends Service {
             await this.limit.limiter.errorIfWouldGoOverLimit('customThemes', {value: '.'});
         } catch (error) {
             if (error.errorType === 'HostLimitError') {
-                return this.modals.open('modals/limit/custom-theme', {
+                return this.modals.open('modals/limits/custom-theme', {
                     message: error.message
                 });
             }

tests/acceptance/settings/design-test.js

@@ -119,6 +119,23 @@ describe('Acceptance: Settings - Design', function () {
     it('can delete installed theme');
 
     describe('limits', function () {
-        it('displays upgrade notice when custom themes are not allowed');
+        it('displays upgrade notice when custom themes are not allowed', async function () {
+            this.server.loadFixtures('configs');
+            const config = this.server.db.configs.find(1);
+            config.hostSettings = {
+                limits: {
+                    customThemes: {
+                        allowlist: ['casper', 'dawn', 'lyra'],
+                        error: 'All our official built-in themes are available the Starter plan, if you upgrade to one of our higher tiers you will also be able to edit and upload custom themes for your site.'
+                    }
+                }
+            };
+            this.server.db.configs.update(1, config);
+
+            await visit('/settings/design/change-theme');
+            await click('[data-test-button="upload-theme"]');
+
+            expect(find('[data-test-modal="limits/custom-theme"]'), 'limits/custom-theme modal').to.exist;
+        });
     });
 });