FIX: Prevent crash importing topics on a tagged embeddable host (#27254)

spec/models/topic_embed_spec.rb

@@ -316,6 +316,36 @@ RSpec.describe TopicEmbed do
       end
     end
 
+    context "when the embeddable host specifies the user and tags" do
+      fab!(:tag1) { Fabricate(:tag, name: "interesting") }
+      fab!(:tag2) { Fabricate(:tag, name: "article") }
+      fab!(:embeddable_host) { Fabricate(:embeddable_host, host: "tag-eviltrout.com") }
+
+      let!(:new_user) { Fabricate(:user) }
+      let(:tags) { [tag1.name, tag2.name] }
+      let(:embed_url_with_tags) { "http://tag-eviltrout.com/abcd" }
+
+      let(:imported_post) do
+        # passing user = system and tags = nil to ensure we're getting the user and tags from the embeddable host
+        # and not from the TopicEmbed.import method in the tests
+        TopicEmbed.import(Discourse.system_user, embed_url_with_tags, title, contents, tags: nil)
+      end
+
+      before do
+        embeddable_host.user = new_user
+        embeddable_host.tags = [tag1, tag2]
+        embeddable_host.save!
+      end
+
+      it "assigns the specified user as the author" do
+        expect(imported_post.user).to eq(new_user)
+      end
+
+      it "associates the specified tags with the topic" do
+        expect(imported_post.topic.tags).to contain_exactly(tag1, tag2)
+      end
+    end
+
     context "when updating an existing post with new tags and a different user" do
       fab!(:tag1) { Fabricate(:tag, name: "interesting") }
       fab!(:tag2) { Fabricate(:tag, name: "article") }