added the pet entity

src/main/java/es/uvigo/esei/daa/entities/Pet.java

 package es.uvigo.esei.daa.entities;
 
+import static java.util.Objects.requireNonNull;
+
 /**
  * Entity that represents a pet from a person
  *
@@ -8,9 +10,70 @@ package es.uvigo.esei.daa.entities;
 public class Pet {
     private int id;
     private String name;
+    private Person owner;
 
     // Constructor needed for the JSON conversion
     Pet() {}
 
+    /**
+     * Constructs a new instance of {@link Pet}.
+     *
+     * @param id identifier of the pet.
+     * @param name name of the pet.
+     * @param owner person who owns the pet.
+     */
+    public Pet(int id, String name, Person owner) {
+        this.id = id;
+        this.setName(name);
+        this.setOwner(owner);
+    }
+
+    /**
+     * Returns the identifier of the pet.
+     *
+     * @return the identifier of the pet.
+     */
+    public int getId() {
+        return id;
+    }
+
+    /**
+     * Returns the name of the pet.
+     *
+     * @return the name of the pet.
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * Set the name of this person.
+     *
+     * @param name the new name of the person.
+     * @throws NullPointerException if the {@code name} is {@code null}.
+     */
+    public void setName(String name) {
+        this.name = requireNonNull(name, "Name can't be null");
+    }
+    /**
+     * Returns the owner of the pet.
+     *
+     * @return the owner of the pet.
+     */
+    public Person getOwner() {
+        return owner;
+    }
+
+    /**
+     * Set the owner of this pet.
+     *
+     * @param owner the owner of the pet.
+     * @throws NullPointerException if the {@code owner} is {@code null}.
+     */
+    public void setOwner(Person owner) {
+        this.owner = requireNonNull(owner, "Owner can't be a null reference");
+    }
+
+
     //TODO -------- ESTABA HACIENDO ESTO MIRAR PRACTICA 2 PARA ENUNCIADO
 }