FEATURE: Inline topic summary. Cached version accessible to everyone. (#22551)

* FEATURE:  Inline topic summary. Cached version accessible to everyone.

Anons and non-members of the `custom_summarization_allowed_groups_map` groups can see cached summaries for any accessible topic. After the first 12 hours and if the posts to summarize have changed, allowed users clicking on the button will automatically re-generate it.

* Ensure chat summaries work and prevent model hallucinations when there are no messages.

spec/requests/topics_controller_spec.rb

@@ -5469,10 +5469,27 @@ RSpec.describe TopicsController do
     end
 
     context "for anons" do
-      it "returns a 404" do
+      it "returns a 404 if there is no cached summary" do
         get "/t/#{topic.id}/strategy-summary.json"
 
-        expect(response.status).to eq(403)
+        expect(response.status).to eq(404)
+      end
+
+      it "returns a cached summary" do
+        section =
+          SummarySection.create!(
+            target: topic,
+            summarized_text: "test",
+            algorithm: "test",
+            original_content_sha: "test",
+          )
+
+        get "/t/#{topic.id}/strategy-summary.json"
+
+        expect(response.status).to eq(200)
+
+        summary = response.parsed_body
+        expect(summary["summary"]).to eq(section.summarized_text)
       end
     end
 
@@ -5498,15 +5515,32 @@ RSpec.describe TopicsController do
       end
     end
 
-    context "when the user is not a member of an allowlited group" do
+    context "when the user is not a member of an allowlisted group" do
       fab!(:user) { Fabricate(:user) }
 
       before { sign_in(user) }
 
-      it "return a 404" do
+      it "return a 404 if there is no cached summary" do
         get "/t/#{topic.id}/strategy-summary.json"
 
-        expect(response.status).to eq(403)
+        expect(response.status).to eq(404)
+      end
+
+      it "returns a cached summary" do
+        section =
+          SummarySection.create!(
+            target: topic,
+            summarized_text: "test",
+            algorithm: "test",
+            original_content_sha: "test",
+          )
+
+        get "/t/#{topic.id}/strategy-summary.json"
+
+        expect(response.status).to eq(200)
+
+        summary = response.parsed_body
+        expect(summary["summary"]).to eq(section.summarized_text)
       end
     end
   end