Extract new relationship instantiation to dedicated methods

This allows you to more easily use your own relationship classes.

Author: JaZo

src/Concerns/HasRelations.php

@@ -34,12 +34,17 @@ public function hasOne(string $itemClass, string $name = null): OneRelationInter
         $name = $name ?: Util::stringSnake(debug_backtrace()[1]['function']);
 
         if (!array_key_exists($name, $this->relations)) {
-            $this->relations[$name] = new HasOneRelation((new $itemClass())->getType());
+            $this->relations[$name] = $this->newHasOne((new $itemClass())->getType());
         }
 
         return $this->relations[$name];
     }
 
+    protected function newHasOne(string $type): OneRelationInterface
+    {
+        return new HasOneRelation($type);
+    }
+
     /**
      * Create a plural relation to another item.
      *
@@ -53,12 +58,17 @@ public function hasMany(string $itemClass, string $name = null): ManyRelationInt
         $name = $name ?: Util::stringSnake(debug_backtrace()[1]['function']);
 
         if (!array_key_exists($name, $this->relations)) {
-            $this->relations[$name] = new HasManyRelation((new $itemClass())->getType());
+            $this->relations[$name] = $this->newHasMany((new $itemClass())->getType());
         }
 
         return $this->relations[$name];
     }
 
+    protected function newHasMany(string $type): ManyRelationInterface
+    {
+        return new HasManyRelation($type);
+    }
+
     /**
      * Create a singular relation.
      *
@@ -71,12 +81,17 @@ public function morphTo(string $name = null): OneRelationInterface
         $name = $name ?: Util::stringSnake(debug_backtrace()[1]['function']);
 
         if (!array_key_exists($name, $this->relations)) {
-            $this->relations[$name] = new MorphToRelation();
+            $this->relations[$name] = $this->newMorphTo();
         }
 
         return $this->relations[$name];
     }
 
+    protected function newMorphTo(): OneRelationInterface
+    {
+        return new MorphToRelation();
+    }
+
     /**
      * Create a plural relation.
      *
@@ -89,12 +104,17 @@ public function morphToMany(string $name = null): ManyRelationInterface
         $name = $name ?: Util::stringSnake(debug_backtrace()[1]['function']);
 
         if (!array_key_exists($name, $this->relations)) {
-            $this->relations[$name] = new MorphToManyRelation();
+            $this->relations[$name] = $this->newMorphToMany();
         }
 
         return $this->relations[$name];
     }
 
+    protected function newMorphToMany(): ManyRelationInterface
+    {
+        return new MorphToManyRelation();
+    }
+
     /**
      * @return \Swis\JsonApi\Client\Interfaces\OneRelationInterface[]|\Swis\JsonApi\Client\Interfaces\ManyRelationInterface[]
      */