feat(user): add user entity and repository with JPA integration

weblog-module-common/build.gradle.kts

@@ -1,5 +1,5 @@
 plugins {
-    java
+    `java-library`
 }
 
 dependencies {
@@ -8,6 +8,8 @@ dependencies {
     implementation("com.google.guava:guava:33.5.0-jre")
     // commons-lang3
     implementation("org.apache.commons:commons-lang3:3.20.0")
+    // jpa
+    api("org.springframework.boot:spring-boot-starter-data-jpa")
     // test
     testImplementation("org.springframework.boot:spring-boot-starter-test")
     // jackson
@@ -17,4 +19,6 @@ dependencies {
     implementation("org.springframework.boot:spring-boot-starter-aop")
     // web
     implementation("org.springframework.boot:spring-boot-starter-web")
+    // postgresql
+    runtimeOnly("org.postgresql:postgresql")
 }