DEV: Add logging and rescue when user already exists and connecting via DiscourseConnect (#22833)

This is happening because despite the user already existing in the forum, the `SingleSignOnRecord` doesn't exist and "require_activation" is set on the provider, causing us to skip looking for the email, and resulting in us creating a new User then seeing Validation failed: Primary email has already been taken when DiscourseConnect is attempting to make a new account.

app/models/discourse_connect.rb

@@ -267,7 +267,16 @@ class DiscourseConnect < DiscourseConnectBase
           ReviewableUser.set_approved_fields!(user, Discourse.system_user)
         end
 
-        user.save!
+        begin
+          user.save!
+        rescue ActiveRecord::RecordInvalid => e
+          if SiteSetting.verbose_discourse_connect_logging
+            Rails.logger.error(
+              "Verbose SSO log: User creation failed. External id: #{external_id}, New User (user_id: #{user.id}) Params: #{user_params} User Params: #{user.attributes} User Errors: #{user.errors.full_messages} Email: #{user.primary_email.attributes} Email Error: #{user.primary_email.errors.full_messages}",
+            )
+          end
+          raise e
+        end
 
         if SiteSetting.verbose_discourse_connect_logging
           Rails.logger.warn(