Add public shareable chats

apps/dbagent/migrations/0008_public-chats.sql

@@ -0,0 +1,21 @@
+CREATE TYPE "public"."visibility" AS ENUM('public', 'private');
+
+--> statement-breakpoint
+CREATE ROLE "anonymous_user";
+
+--> statement-breakpoint
+ALTER TABLE
+    "chats"
+ADD
+    COLUMN "visibility" "visibility" DEFAULT 'private' NOT NULL;
+
+--> statement-breakpoint
+CREATE POLICY "chats_anonymous_policy" ON "chats" AS PERMISSIVE FOR
+SELECT
+    TO "anonymous_user" USING (visibility = 'public');
+
+--> statement-breakpoint
+GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO "anonymous_user";
+
+--> statement-breakpoint
+ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT ALL PRIVILEGES ON TABLES TO "anonymous_user";