refactor: providerId 문자열로 수정

providerId는 문자열 + 숫자 조합이라 문자열로 저장해야함.

Author: sapiens2000

src/main/java/com/example/log4u/domain/diary/controller/DiaryController.java

@@ -83,7 +83,7 @@ private User mockUser() {
 		return User.builder()
 			.userId(1L)
 			.nickname("목유저")
-			.providerId(12345L)
+			.providerId("12345")
 			.provider("MOCK")
 			.email("[email protected]")
 			.statusMessage("목유저입니다.")

src/main/java/com/example/log4u/domain/user/entity/User.java

@@ -5,8 +5,6 @@
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
-import jakarta.persistence.EnumType;
-import jakarta.persistence.Enumerated;
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
@@ -43,9 +41,6 @@ public class User extends BaseEntity {
 	@Column(nullable = false)
 	private String providerId;
 
-	@Column(nullable = false)
-	private String provider;
-
 	private String profileImageUrl;
 
 	@Column(nullable = false)