feat: add key-value store service with CRUD operations

- Implemented set, get, del, exists, and keys functions for managing key-value pairs in the KV store.
- Added error handling for each function to ensure robustness.
- Utilized jsonb for value storage, allowing for flexible data types.
- Created a new migration snapshot for the database schema including the kv table.

Author: kingRayhan

migrations/0001_equal_mandroid.sql

@@ -0,0 +1,5 @@
+CREATE TABLE "kv" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"key" uuid,
+	"value" json
+);

migrations/0002_high_rage.sql

@@ -0,0 +1,3 @@
+ALTER TABLE "kv" ALTER COLUMN "key" SET DATA TYPE text;--> statement-breakpoint
+ALTER TABLE "kv" ALTER COLUMN "key" SET NOT NULL;--> statement-breakpoint
+ALTER TABLE "kv" ADD CONSTRAINT "kv_key_unique" UNIQUE("key");

migrations/0003_flimsy_ezekiel.sql

@@ -0,0 +1 @@
+ALTER TABLE "kv" ALTER COLUMN "value" SET DATA TYPE jsonb;