Add Post representation using JPA

JPA Entities are POJOs associated to data that can be persisted to
database. `Post` Entity represents a table of posts in the DB. Therefore
an instance of a `Post` can be used to manage a row in this table.

PostRepository it's an interface that extends JPARepository. By doing that, it
inherits different methods that can be used for common persistence operations.

myapp/src/main/java/com/example/myapp/Post.java

@@ -0,0 +1,40 @@
+package com.example.myapp;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class Post {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+    private String title;
+    private String content;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public String getContent() {
+        return content;
+    }
+
+    public void setContent(String content) {
+        this.content = content;
+    }
+}

myapp/src/main/java/com/example/myapp/PostRepository.java

@@ -0,0 +1,6 @@
+package com.example.myapp;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface PostRepository extends JpaRepository<Post, Long> {
+}