feat: Implement get app auth API endpoint

packages/backend/test/mocks/rest/api/v1/apps/get-auth.js

@@ -0,0 +1,18 @@
+const getAuthMock = (auth) => {
+  return {
+    data: {
+      fields: auth.fields,
+      authenticationSteps: auth.authenticationSteps,
+      reconnectionSteps: auth.reconnectionSteps,
+    },
+    meta: {
+      count: 1,
+      currentPage: null,
+      isArray: false,
+      totalPages: null,
+      type: 'Object',
+    },
+  };
+};
+
+export default getAuthMock;