Update serializers.py

-from django.contrib.auth.models import User, Group
 from rest_framework import serializers
-from api.models import Item, SharedItem
+from api.models import User
 
 
-class UserSerializer(serializers.HyperlinkedModelSerializer):
+class UserSerializer(serializers.ModelSerializer):
     class Meta:
         model = User
-        fields = ['url', 'username', 'email', 'groups']
+        fields = '__all__'
+
+
+class SignUpSerializer(serializers.ModelSerializer):
+    password2 = serializers.CharField(style={"input_type": "password"})
 
-class GroupSerializer(serializers.HyperlinkedModelSerializer):
     class Meta:
-        model = Group
-        fields = ['url', 'name']
+        model = User
+        fields = ['user_id', 'name', 'password', 'password2']
+
+    def create(self, data):
+        user_id = data['user_id']
+        name = data['name']
+        password = self.data['password']
+        password2 = self.data['password2']
+
+        if user_id and User.objects.filter(user_id=user_id).exclude(name=name).exists():
+            raise serializers.ValidationError({"user_id": "User_id must be unique."})
 
-class ItemSerializer(serializers.ModelSerializer):
+        elif password != password2:
+            raise serializers.ValidationError({'password': "Passwords must match."})
+
+        user = User.objects.create(
+            user_id=data['user_id'],
+            name=data['name'],
+            password=data['password'],
+        )
+        user.save()
+
+        return user
+
+
+class UserInfoSerializer(serializers.ModelSerializer):
     class Meta:
-        model = Item
-        fields = '__all__'
+        model = User
+        fields = ['user_id', 'name', 'total_size', 'current_size']