Add index on role.name (#294)

Co-authored-by: Qianmian Yu <im.qianmian.yu@gmail.com>

eladmin-system/src/main/java/me/zhengjie/modules/system/domain/Role.java

@@ -18,7 +18,8 @@ import java.util.Set;
  * @date 2018-11-22
  */
 @Entity
-@Table(name = "role")
+@Table(name = "role",
+        indexes = {@Index(name = "role_name_index", columnList = "name")})
 @Getter
 @Setter
 public class Role implements Serializable {