[Route("/me/login/")]
public class LoginRequest : IReturn<LoginResponse>
{
    public string password { get; internal set; }
    public string username { get; internal set; }
}

public class LoginResponse
{
    public string token { get; set; }
}

client.PostAsync(new LoginRequest { username = email, password = password });

{
    "non_field_errors": [
        "Unable to login with the given credentials."
    ]
}