DEV: Hash tokens stored from email_tokens (#14493)

This commit adds token_hash and scopes columns to email_tokens table.
token_hash is a replacement for the token column to avoid storing email
tokens in plaintext as it can pose a security risk. The new scope column
ensures that email tokens cannot be used to perform a different action
than the one intended.

To sum up, this commit:

* Adds token_hash and scope to email_tokens

* Reuses code that schedules critical_user_email

* Refactors EmailToken.confirm and EmailToken.atomic_confirm methods

* Periodically cleans old, unconfirmed or expired email tokens

app/services/user_authenticator.rb

@@ -49,10 +49,7 @@ class UserAuthenticator
   private
 
   def confirm_email
-    if authenticated?
-      EmailToken.confirm(@user.email_tokens.first.token)
-      @user.set_automatic_groups
-    end
+    @user.activate if authenticated?
   end
 
   def authenticator