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)
}
`;
```

Review the mutation section linked in the issue, the generated pages/__generated__/login.ts file, and server/src/__tests__/integration.js. Check that the mutation naming and generated type references use the same casing throughout; the tutorial code and integration test should be consistent and no longer produce the reported errors.

Written by the indexing model from the issue text.