feat: RecommendedPost 엔티티 추가

#1397

backend/src/main/java/wooteco/prolog/roadmap/domain/Keyword.java

@@ -8,10 +8,7 @@
 import wooteco.prolog.roadmap.exception.KeywordSeqException;
 
 import javax.persistence.*;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Objects;
-import java.util.Set;
+import java.util.*;
 
 @Getter
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
@@ -36,10 +33,8 @@ public class Keyword {
     @Column(name = "session_id", nullable = false)
     private Long sessionId;
 
-    @ElementCollection
-    @CollectionTable(name = "keyword_reference")
-    @Column(name = "url")
-    private List<String> references;
+    @OneToMany(mappedBy = "keyword", cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.EAGER)
+    private List<RecommendedPost> recommendedPosts = new ArrayList<>();
 
     @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name = "parent_id")

backend/src/main/java/wooteco/prolog/roadmap/domain/RecommendedPost.java

@@ -0,0 +1,62 @@
+package wooteco.prolog.roadmap.domain;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+import java.util.Objects;
+
+@Entity
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+@AllArgsConstructor
+@Getter
+public class RecommendedPost {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false)
+    private String url;
+
+    @ManyToOne
+    @JoinColumn(nullable = false)
+    private Keyword keyword;
+
+    public RecommendedPost(final String url) {
+        this(null, url, null);
+    }
+
+    public void updateUrl(final String url) {
+        this.url = url;
+    }
+
+    public void remove() {
+        if (this.keyword == null) {
+            return;
+        }
+
+        keyword.getRecommendedPosts().remove(this);
+        this.keyword = null;
+    }
+
+    public void addKeyword(final Keyword keyword) {
+        this.keyword = keyword;
+        keyword.getRecommendedPosts().add(this);
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) return true;
+        if (!(o instanceof RecommendedPost)) return false;
+        final RecommendedPost post = (RecommendedPost) o;
+        return Objects.equals(id, post.id);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id);
+    }
+}

backend/src/main/resources/db/migration/prod/V4__alter_table_keyword_reference.sql

@@ -0,0 +1,10 @@
+drop table prolog.keyword_reference;
+
+create table if not exists prolog.recommended_post
+(
+    id         bigint auto_increment primary key,
+    url        varchar(255) not null,
+    keyword_id bigint       not null,
+    constraint FK_KEYWORD_ID
+        foreign key (keyword_id) references prolog.keyword (id)
+);