chore: Update LLM formatter classes to include additional details (#11491)

This PR introduces support for optionally exposing more data during LLM
function calls. This will be useful as we expand Copilot’s capabilities.

Changes included:
- Add support for ArticleLlmFormatter
- Add missing specs for ContactLLMFormatter and ArticleLLMFormatter
- Add additional spec for ConversationLLMFormatter based on config

app/services/llm_formatter/article_llm_formatter.rb

@@ -0,0 +1,22 @@
+class LlmFormatter::ArticleLlmFormatter
+  attr_reader :article
+
+  def initialize(article)
+    @article = article
+  end
+
+  def format(*)
+    <<~TEXT
+      Title: #{article.title}
+      ID: #{article.id}
+      Status: #{article.status}
+      Category: #{article.category&.name || 'Uncategorized'}
+      Author: #{article.author&.name || 'Unknown'}
+      Views: #{article.views}
+      Created At: #{article.created_at}
+      Updated At: #{article.updated_at}
+      Content:
+      #{article.content}
+    TEXT
+  end
+end