feat: User Entity 생성 (#1)

classmate-backend-main/classmate/src/main/java/devteamOne/classmate/user/domain/User.java

@@ -0,0 +1,31 @@
+package devteamOne.classmate.user.domain;
+
+import devteamOne.classmate.channel.domain.Channel;
+import devteamOne.classmate.question.domain.Question;
+import jakarta.persistence.*;
+import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnJava;
+
+@Entity
+public class User {
+
+  @Id
+  @GeneratedValue(strategy = GenerationType.IDENTITY)
+  private Long id;
+
+  private String nickname;
+
+  private String socialId;
+
+  private String provider;
+
+  private LocalDateTime createdAt;
+
+  @OneToMany(mappedBy = "user")
+  private List<Channel> channelList = new ArrayList<>();
+
+  @OneToMany(mappedBy = "user")
+  private List<Question> questionList = new ArrayList<>();
+}