FIX: Rejection email sent even if reject reason too long (#27529)

Followup 6b872c4c53

Even though we were showing a validation error for a reject
reason that was too long, we were still sending an email and
doing other operations on the user which we are rejecting.

This commit fixes this by validating the reviewable model
before attempting to do anything else after the reason is set.

app/models/reviewable_user.rb

@@ -46,6 +46,9 @@ class ReviewableUser < Reviewable
       begin
         self.reject_reason = args[:reject_reason]
 
+        # Without this, we end up sending the email even if this reject_reason is too long.
+        self.validate!
+
         if args[:send_email] && SiteSetting.must_approve_users?
           # Execute job instead of enqueue because user has to exists to send email
           Jobs::CriticalUserEmail.new.execute(

spec/requests/reviewables_controller_spec.rb

@@ -187,7 +187,7 @@ RSpec.describe ReviewablesController do
         expect(json["errors"][0]).to eq(I18n.t("reviewables.already_handled_and_user_not_exist"))
       end
 
-      it "returns a readable error message if reject_reason is too long" do
+      it "returns a readable error message if reject_reason is too long, does not send email, and does not delete the user" do
         sign_in(admin)
         Jobs.run_immediately!
         SiteSetting.must_approve_users = true
@@ -195,11 +195,14 @@ RSpec.describe ReviewablesController do
         user.activate
         reviewable = ReviewableUser.find_by(target: user)
 
+        expect {
           put "/review/#{reviewable.id}/perform/delete_user.json?version=0",
               params: {
                 send_email: true,
                 reject_reason: "a" * 3000,
               }
+        }.to not_change { ActionMailer::Base.deliveries.size }.and not_change { User.count }
+
         expect(response.code).to eq("422")
         expect(response.parsed_body["errors"]).to eq(
           ["Reject reason " + I18n.t("errors.messages.too_long", count: 2000)],