Change Model#addPerson(...) signature to ReadOnlyPerson

Model#addPerson(Person) accepts a mutable Person object. Outside
classes are able to modify the Person object after inserting it into
the model.

Only Model should be able to modify the Person objects that it owns.

Let's change addPerson()'s signature from Person to ReadOnlyPerson, so
that the internal Person list is forced to duplicate this object,
satisfying our new constraint.

src/main/java/seedu/address/model/Model.java

@@ -3,7 +3,6 @@
 import java.util.Set;
 
 import seedu.address.commons.core.UnmodifiableObservableList;
-import seedu.address.model.person.Person;
 import seedu.address.model.person.ReadOnlyPerson;
 import seedu.address.model.person.UniquePersonList;
 import seedu.address.model.person.UniquePersonList.DuplicatePersonException;
@@ -22,7 +21,7 @@ public interface Model {
     void deletePerson(ReadOnlyPerson target) throws UniquePersonList.PersonNotFoundException;
 
     /** Adds the given person */
-    void addPerson(Person person) throws UniquePersonList.DuplicatePersonException;
+    void addPerson(ReadOnlyPerson person) throws UniquePersonList.DuplicatePersonException;
 
     /**
      * Updates the person located at {@code filteredPersonListIndex} with {@code editedPerson}.

src/main/java/seedu/address/model/ModelManager.java

@@ -10,7 +10,6 @@
 import seedu.address.commons.events.model.AddressBookChangedEvent;
 import seedu.address.commons.util.CollectionUtil;
 import seedu.address.commons.util.StringUtil;
-import seedu.address.model.person.Person;
 import seedu.address.model.person.ReadOnlyPerson;
 import seedu.address.model.person.UniquePersonList;
 import seedu.address.model.person.UniquePersonList.PersonNotFoundException;
@@ -65,7 +64,7 @@ public synchronized void deletePerson(ReadOnlyPerson target) throws PersonNotFou
     }
 
     @Override
-    public synchronized void addPerson(Person person) throws UniquePersonList.DuplicatePersonException {
+    public synchronized void addPerson(ReadOnlyPerson person) throws UniquePersonList.DuplicatePersonException {
         addressBook.addPerson(person);
         updateFilteredListToShowAll();
         indicateAddressBookChanged();

src/test/java/seedu/address/logic/commands/AddCommandTest.java

@@ -69,7 +69,7 @@ private AddCommand getAddCommandForPerson(Person person, Model model) throws Ill
      */
     private class ModelStub implements Model {
         @Override
-        public void addPerson(Person person) throws DuplicatePersonException {
+        public void addPerson(ReadOnlyPerson person) throws DuplicatePersonException {
             fail("This method should not be called.");
         }
 
@@ -117,7 +117,7 @@ public void updateFilteredPersonList(Set<String> keywords) {
      */
     private class ModelStubThrowingDuplicatePersonException extends ModelStub {
         @Override
-        public void addPerson(Person person) throws DuplicatePersonException {
+        public void addPerson(ReadOnlyPerson person) throws DuplicatePersonException {
             throw new DuplicatePersonException();
         }
     }
@@ -129,8 +129,8 @@ private class ModelStubAcceptingPersonAdded extends ModelStub {
         final ArrayList<Person> personsAdded = new ArrayList<>();
 
         @Override
-        public void addPerson(Person person) throws DuplicatePersonException {
-            personsAdded.add(person);
+        public void addPerson(ReadOnlyPerson person) throws DuplicatePersonException {
+            personsAdded.add(new Person(person));
         }
     }