Login __generated__ file with mutation defined in lowercase is causing errors

Following the official documentation and the rest of the tutorial, queries and mutations are defined with the first letter in uppercase (PascalCase). However, in this [part of the tutorial](https://www.apollographql.com/docs/tutorial/mutations/#define-the-mutation) the mutation `Login` is defined lowercase (I see that in the final version of the tutorial this is corrected):

```gql
export const LOGIN_USER = gql`
mutation login($email: String!) {
login(email: $email)
}
`;
```

The corresponding generated file (`pages/__generated__/login.ts`), `Login` type appears as well in lowercase but the related code is assuming they are in uppercase, throwing errors:

```gql
const [login, { loading, error }] = useMutation<
LoginTypes.Login,
LoginTypes.LoginVariables
>(LOGIN_USER);
```

The mutation `Login` in the integration tests (`server/src/__tests__/integration.js`) is also defined in lowercase:
```gql
const LOGIN = gql`
mutation login($email: String!) {
login(email: $email)
}
`;
```

Revisa la sección de mutation enlazada en el issue, el archivo generado pages/__generated__/login.ts y server/src/__tests__/integration.js. Comprueba que el nombre de la mutation y las referencias a los tipos generados usen la misma combinación de mayúsculas y minúsculas en todo momento; el código del tutorial y la prueba de integración deben ser coherentes y dejar de producir los errores indicados.

Escrito por el modelo de indexación a partir del texto del issue.