feat: create pawn class and handle his associations.

Handled associations: Pawn-Square and Pawn-Tracked.

not-alone-server/src/main/java/fr/univnantes/alma/model/Pawn.java

+package fr.univnantes.alma.model;
+
+import fr.univnantes.alma.model.player.Creature;
+import fr.univnantes.alma.model.player.Tracked;
+import fr.univnantes.alma.model.square.Square;
+import fr.univnantes.alma.references.associations.BidirectionalManyToOne;
+import fr.univnantes.alma.references.associations.BidirectionalOneToOne;
+import fr.univnantes.alma.references.interfaces.ManyToOneAssociation;
+import fr.univnantes.alma.references.interfaces.OneToOneAssociation;
+
+/**
+ * Pawn used by the tracked.
+ */
+public class Pawn {
+    /**
+     * Associated square.
+     */
+    private OneToOneAssociation<Pawn, Square> square;
+
+    /**
+     * Owner of the card (Creature hand).
+     */
+    private ManyToOneAssociation<Pawn, Tracked> owner;
+    /**
+     * Create new Pawn.
+     */
+    public Pawn() {
+        square = new BidirectionalOneToOne<>(this, Square::getPawn);
+        owner = new BidirectionalManyToOne<>(this, Tracked::getPawns);
+    }
+
+    /**
+     * Return the associated square to the pawn.
+     * @return Square.
+     */
+    public OneToOneAssociation<Pawn, Square> getSquare() {
+        return square;
+    }
+
+    /**
+     * Return pawn owner.
+     * @return Tracked
+     */
+    public ManyToOneAssociation<Pawn, Tracked> getOwner() {
+        return owner;
+    }
+}

not-alone-server/src/main/java/fr/univnantes/alma/model/player/Tracked.java

 package fr.univnantes.alma.model.player;
 
+import fr.univnantes.alma.model.Pawn;
 import fr.univnantes.alma.model.card.place.PlaceCard;
 import fr.univnantes.alma.references.associations.BidirectionalOneToMany;
 import fr.univnantes.alma.references.interfaces.OneToManyAssociation;
@@ -18,6 +19,12 @@ public class Tracked extends Player {
      * Tracked player discard.
      */
     private OneToManyAssociation<Tracked, PlaceCard> discard;
+
+    /**
+     * Tracked player discard.
+     */
+    private OneToManyAssociation<Tracked, Pawn> pawns;
+
     /**
      * Create new Tracked Player.
      * By default, player is UNBLOCKED.
@@ -30,6 +37,7 @@ public class Tracked extends Player {
         hand = new BidirectionalOneToMany<>(this, PlaceCard::getHandOwner);
         discard = new BidirectionalOneToMany<>(this,
                                 PlaceCard::getDiscardOwner);
+        pawns = new BidirectionalOneToMany<>(this, Pawn::getOwner);
     }
 
     /**
@@ -48,4 +56,11 @@ public class Tracked extends Player {
         return discard;
     }
 
+    /**
+     * Return pawns.
+     * @return Pawns
+     */
+    public OneToManyAssociation<Tracked, Pawn> getPawns() {
+        return pawns;
+    }
 }

not-alone-server/src/main/java/fr/univnantes/alma/model/square/Square.java

 package fr.univnantes.alma.model.square;
 
+import fr.univnantes.alma.model.Pawn;
+import fr.univnantes.alma.references.associations.BidirectionalOneToOne;
+import fr.univnantes.alma.references.interfaces.OneToOneAssociation;
+
 /***
  * Game board square.
  */
@@ -10,12 +14,18 @@ public abstract class Square {
      */
     private int position;
 
+    /**
+     * Associated square.
+     */
+    private OneToOneAssociation<Square, Pawn> pawn;
+
     /**
      * Create new instance of Square.
      * @param squarePosition square position
      */
     public Square(final int squarePosition) {
         this.position = squarePosition;
+        pawn = new BidirectionalOneToOne<>(this, Pawn::getSquare);
     }
 
     /**
@@ -25,4 +35,12 @@ public abstract class Square {
     public int getPosition() {
         return position;
     }
+
+    /**
+     * Return associated pawn to the square.
+     * @return Pawn
+     */
+    public OneToOneAssociation<Square, Pawn> getPawn() {
+        return pawn;
+    }
 }