add mongodb dependency

sth-backend/pom.xml

@@ -65,6 +65,11 @@
 			<artifactId>log4j-core</artifactId>
 			<version>2.22.0</version>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-mongodb</artifactId>
+		</dependency>
+
 	</dependencies>
 
 	<build>