SUPPORT-8957: add service and controller for user management

backend/pom.xml

@@ -216,6 +216,14 @@
       <groupId>org.postgresql</groupId>
       <artifactId>postgresql</artifactId>
     </dependency>
+    <dependency>
+      <groupId>javax.validation</groupId>
+      <artifactId>validation-api</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.hibernate.validator</groupId>
+      <artifactId>hibernate-validator</artifactId>
+    </dependency>
   </dependencies>
   <build>
     <finalName>${project.parent.artifactId}</finalName>