FIX: Update spam controller action should consider seeded LLM properly (

#1053)

The seeded LLM setting: `SiteSetting.ai_spam_detection_model_allowed_seeded_models` returns a _string_ with IDs separated by pipes. running `_map` on it will return an array with strings. We were previously checking for the id with custom prefix identifier, but instead we should be checking the stringified ID.

app/controllers/discourse_ai/admin/ai_spam_controller.rb

@@ -15,7 +15,7 @@ def update
           llm_model_id = updated_params[:llm_model_id] = allowed_params[:llm_model_id]
           if llm_model_id.to_i < 0 &&
                !SiteSetting.ai_spam_detection_model_allowed_seeded_models_map.include?(
-                 "custom:#{llm_model_id}",
+                 llm_model_id.to_s,
                )
             return(
               render_json_error(

spec/requests/admin/ai_spam_controller_spec.rb

@@ -37,7 +37,7 @@
 
         expect(response.status).to eq(422)
 
-        SiteSetting.ai_spam_detection_model_allowed_seeded_models = seeded_llm.identifier
+        SiteSetting.ai_spam_detection_model_allowed_seeded_models = seeded_llm.id.to_s
 
         put "/admin/plugins/discourse-ai/ai-spam.json",
             params: {
@@ -49,6 +49,26 @@
         expect(response.status).to eq(200)
       end
 
+      it "ensures that seeded llm ID is properly passed and allowed" do
+        seeded_llm = Fabricate(:seeded_model)
+
+        SiteSetting.ai_spam_detection_model_allowed_seeded_models = [
+          llm_model.id,
+          seeded_llm.id,
+        ].join("|")
+
+        put "/admin/plugins/discourse-ai/ai-spam.json",
+            params: {
+              is_enabled: true,
+              llm_model_id: seeded_llm.id,
+              custom_instructions: "custom instructions",
+            }
+        expect(SiteSetting.ai_spam_detection_model_allowed_seeded_models).to eq(
+          "#{llm_model.id}|#{seeded_llm.id}",
+        )
+        expect(response.status).to eq(200)
+      end
+
       it "can not enable spam detection without a model selected" do
         put "/admin/plugins/discourse-ai/ai-spam.json",
             params: {