Move some interactions to the backendInteractor

The idea is that all interactions should move there, so components
don't have to pass around credentials all the time.

src/modules/api.js

@@ -0,0 +1,14 @@
+import backendInteractorService from '../services/backend_interactor_service/backend_interactor_service.js'
+
+const api = {
+  state: {
+    backendInteractor: backendInteractorService()
+  },
+  mutations: {
+    setBackendInteractor (state, backendInteractor) {
+      state.backendInteractor = backendInteractor
+    }
+  }
+}
+
+export default api