Disabling /register is possible;
app.MapGroup("/account").MapIdentityApi<User>();
app.UseAuthorization();
app.Use(async (context, next) =>
{
#if DEBUG
await next.Invoke();
#else
//if we are in prod then return 404 for register endpoint
if (context.Request.Path.ToString().StartsWith("/account/register"))
{
context.Response.StatusCode = 404;
await context.Response.CompleteAsync();
}
else
{
await next.Invoke();
}
#endif
});