enable jpa library for managing data

backend/build.gradle.kts

@@ -17,6 +17,7 @@ repositories {
 
 dependencies {
 	implementation("org.springframework.boot:spring-boot-starter-jdbc")
+	implementation("org.springframework.boot:spring-boot-starter-data-jpa")
 	implementation("org.springframework.boot:spring-boot-starter-mail")
 	implementation("org.springframework.boot:spring-boot-starter-web")
 	// implementation("org.springframework.session:spring-session-jdbc")