Hello, I am tring to use IdentityUser to impliment auth I tried

Question

Hello, I am tring to use IdentityUser to impliment auth I tried

to use MapIdentityApi
but it can not be configured,

So I copy past the code and customze it for the app needs

My problems is I want to send email confiramtion 'code' instead of 'link'

The code generated and send in the link parameter is too long (because it is token) so I can not use it, and I did nkt find any way to store my custom code (let's say a 6-digit int) using the userManager

So I tried to impliment my custom code verification,

But obviousy, it contains venurabilites that I can't notice,

So My question :
Is there any build-in feature on userIdentity that I can use?
Or a secure package?