FIX: Skip tags-related validations when the skip_validations option is present (#26379)

The `TopicCreator` class has a `skip_validations` option that can force-create a topic without performing permission checks or validation rules. However, at the moment it doesn't skip validations that are related to tags, so topics that are created by the system or by some scrip can still fail if they use tags. This commit makes the `TopicCreator` class skip all tags-related checks if the `skip_validations` is specified.

Internal topic: t/124280.

spec/lib/topic_creator_spec.rb

@@ -150,6 +150,27 @@ RSpec.describe TopicCreator do
         end
       end
 
+      context "with skip_validations option" do
+        it "allows the user to add tags even if they're not permitted" do
+          SiteSetting.tag_topic_allowed_groups = Group::AUTO_GROUPS[:trust_level_2]
+          user.update!(trust_level: TrustLevel[1])
+          Group.user_trust_level_change!(user.id, user.trust_level)
+          topic =
+            TopicCreator.create(
+              user,
+              Guardian.new(user),
+              valid_attrs.merge(
+                title: "This is a valid title",
+                raw: "Somewhat lengthy body for my cool topic",
+                tags: [tag1.name, tag2.name, "brandnewtag434"],
+                skip_validations: true,
+              ),
+            )
+          expect(topic).to be_persisted
+          expect(topic.tags.pluck(:name)).to contain_exactly(tag1.name, tag2.name, "brandnewtag434")
+        end
+      end
+
       context "with staff-only tags" do
         before { create_staff_only_tags(["alpha"]) }