feat: implement create-chat-conversation function with OpenAI integration and Supabase support

- Added CORS handling for the create-chat-conversation function.
- Implemented health check endpoint for the function.
- Created endpoints for managing conversations and messages with OpenAI.
- Added error handling and response formatting for better API usability.
- Introduced utility functions for environment variable management and Supabase client creation.
- Enhanced schema handling for structured responses from OpenAI.
- Implemented conversation archiving and retrieval logic.

supabase/functions/create-chat-conversation/lib/env.ts

@@ -0,0 +1,9 @@
+export function mustGetEnv(name: string): string {
+  const v = Deno.env.get(name);
+  if (!v) throw new Error(`Missing env var: ${name}`);
+  return v;
+}
+
+export function getEnv(name: string, fallback?: string): string | undefined {
+  return Deno.env.get(name) ?? fallback;
+}