feat: Url 레포지토리 작성

src/main/java/com/prgrmrs/urlshortener/repository/UrlRepository.java

@@ -0,0 +1,10 @@
+package com.prgrmrs.urlshortener.repository;
+
+import com.prgrmrs.urlshortener.model.UrlMapping;
+import java.util.Optional;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface UrlRepository extends JpaRepository<UrlMapping, Long> {
+
+    Optional<UrlMapping> findByHash(String hash);
+}