Simple Graphql CRUD operations
mutation { addUser(emailId: "xyz@gmail.com", userName: "xyz", password: "zyx") { userName } }
mutation { deleteUser(emailId: "xyzs@gmail.com") { emailId } }
mutation { updateUser(emailId: "xyz@gmail.com", newUserName: "new_xyz") { userName } }
{ user(emailId: "xyz@gmail.com") { userName } }