feat: created Repository

src/main/java/edu/group5/app/model/Repository.java

@@ -1,4 +1,25 @@
 package edu.group5.app.model;
 
-public class Repository {
+/**
+ * Represents a repository.
+ */
+public abstract class Repository {
+  /**
+   * The underlying data structure that holds the repository's content.
+   */
+  protected Object content;
+
+  /**
+   * Constructs a new Repository with the specified content.
+   *
+   * @param content the underlying data structure used to store entities
+   */
+  protected Repository(Object content) {
+    this.content = content;
+  }
+
+  /**
+   * @return content of the repo
+   */
+  public abstract Object getContent();
 }