[Refactor] Cleanup agent store and actions (#373)

* Cleanup agent store and actions

* Move set/create/update/destroy to helpers

* Update mutation specs

* Add specs for API helper

* Fix edit/delete action visibility

* Add actions specs

* Remove unused API helpers

* Remove duplicates

* Remove duplicates

* Fix duplicate

app/javascript/dashboard/api/specs/agents.spec.js

@@ -0,0 +1,13 @@
+import agents from '../agents';
+import ApiClient from '../ApiClient';
+
+describe('#AgentAPI', () => {
+  it('creates correct instance', () => {
+    expect(agents).toBeInstanceOf(ApiClient);
+    expect(agents).toHaveProperty('get');
+    expect(agents).toHaveProperty('show');
+    expect(agents).toHaveProperty('create');
+    expect(agents).toHaveProperty('update');
+    expect(agents).toHaveProperty('delete');
+  });
+});