refactor(serializers): Move base serializers to core app

Relocate base serializers for users, promos, and comments from the `user` and `business` apps to the central `core` app. This change promotes code reuse and establishes a more logical and scalable project structure.

- Moved `BaseUserSerializer`, `BaseUserPromoSerializer`, and `BaseCommentSerializer` to `core/serializers.py`.
- Renamed `BasePromoSerializer` to `BaseCompanyPromoSerializer` for clarity.
- Updated all dependent serializers in the `user` and `business` apps to inherit from the new centralized base classes in `core`.

Author: RandomProgramm3r

promo_code/business/serializers.py

@@ -173,14 +173,16 @@ def to_internal_value(self, data):
         return super().to_internal_value(data)
 
 
-class PromoCreateSerializer(core.serializers.BasePromoSerializer):
+class PromoCreateSerializer(core.serializers.BaseCompanyPromoSerializer):
     url = rest_framework.serializers.HyperlinkedIdentityField(
         view_name='api-business:promo-detail',
         lookup_field='id',
     )
 
-    class Meta(core.serializers.BasePromoSerializer.Meta):
-        fields = ('url',) + core.serializers.BasePromoSerializer.Meta.fields
+    class Meta(core.serializers.BaseCompanyPromoSerializer.Meta):
+        fields = (
+            'url',
+        ) + core.serializers.BaseCompanyPromoSerializer.Meta.fields
 
     def create(self, validated_data):
         target_data = validated_data.pop('target')
@@ -225,7 +227,7 @@ def validate(self, attrs):
         return attrs
 
 
-class PromoDetailSerializer(core.serializers.BasePromoSerializer):
+class PromoDetailSerializer(core.serializers.BaseCompanyPromoSerializer):
     promo_id = rest_framework.serializers.UUIDField(
         source='id',
         read_only=True,
@@ -253,8 +255,8 @@ class PromoDetailSerializer(core.serializers.BasePromoSerializer):
 
     promo_unique = rest_framework.serializers.SerializerMethodField()
 
-    class Meta(core.serializers.BasePromoSerializer.Meta):
-        fields = core.serializers.BasePromoSerializer.Meta.fields + (
+    class Meta(core.serializers.BaseCompanyPromoSerializer.Meta):
+        fields = core.serializers.BaseCompanyPromoSerializer.Meta.fields + (
             'promo_id',
             'company_name',
             'like_count',

promo_code/core/serializers.py

@@ -1,9 +1,12 @@
+import django.contrib.auth.password_validation
 import pycountry
 import rest_framework.exceptions
 import rest_framework.serializers
 
 import business.constants
 import business.models
+import user.constants
+import user.models
 
 
 class BaseLimitOffsetPaginationSerializer(
@@ -96,7 +99,7 @@ def validate(self, data):
         return data
 
 
-class BasePromoSerializer(rest_framework.serializers.ModelSerializer):
+class BaseCompanyPromoSerializer(rest_framework.serializers.ModelSerializer):
     """
     Base serializer for promo, containing validation and representation logic.
     """
@@ -278,3 +281,140 @@ def to_representation(self, instance):
             data.pop('promo_unique', None)
 
         return data
+
+
+class OtherFieldSerializer(rest_framework.serializers.Serializer):
+    age = rest_framework.serializers.IntegerField(
+        required=True,
+        min_value=user.constants.AGE_MIN,
+        max_value=user.constants.AGE_MAX,
+    )
+    country = CountryField(required=True)
+
+
+class BaseUserSerializer(rest_framework.serializers.ModelSerializer):
+    password = rest_framework.serializers.CharField(
+        write_only=True,
+        required=True,
+        validators=[django.contrib.auth.password_validation.validate_password],
+        max_length=user.constants.PASSWORD_MAX_LENGTH,
+        min_length=user.constants.PASSWORD_MIN_LENGTH,
+        style={'input_type': 'password'},
+    )
+    name = rest_framework.serializers.CharField(
+        required=True,
+        min_length=user.constants.NAME_MIN_LENGTH,
+        max_length=user.constants.NAME_MAX_LENGTH,
+    )
+    surname = rest_framework.serializers.CharField(
+        required=True,
+        min_length=user.constants.SURNAME_MIN_LENGTH,
+        max_length=user.constants.SURNAME_MAX_LENGTH,
+    )
+    email = rest_framework.serializers.EmailField(
+        required=True,
+        min_length=user.constants.EMAIL_MIN_LENGTH,
+        max_length=user.constants.EMAIL_MAX_LENGTH,
+    )
+    avatar_url = rest_framework.serializers.URLField(
+        required=False,
+        max_length=user.constants.AVATAR_URL_MAX_LENGTH,
+        allow_null=True,
+    )
+    other = OtherFieldSerializer(required=True)
+
+    class Meta:
+        model = user.models.User
+        fields = (
+            'name',
+            'surname',
+            'email',
+            'password',
+            'avatar_url',
+            'other',
+        )
+
+
+class BaseUserPromoSerializer(rest_framework.serializers.ModelSerializer):
+    """
+    Base serializer for promos, containing common fields and methods.
+    """
+
+    promo_id = rest_framework.serializers.UUIDField(source='id')
+    company_id = rest_framework.serializers.UUIDField(source='company.id')
+    company_name = rest_framework.serializers.CharField(source='company.name')
+    active = rest_framework.serializers.BooleanField(source='is_active')
+    like_count = rest_framework.serializers.IntegerField(
+        source='get_like_count',
+    )
+    comment_count = rest_framework.serializers.IntegerField(
+        source='get_comment_count',
+    )
+
+    is_liked_by_user = rest_framework.serializers.SerializerMethodField()
+    is_activated_by_user = rest_framework.serializers.SerializerMethodField()
+
+    class Meta:
+        model = business.models.Promo
+        fields = (
+            'promo_id',
+            'company_id',
+            'company_name',
+            'description',
+            'image_url',
+            'active',
+            'is_activated_by_user',
+            'like_count',
+            'comment_count',
+            'is_liked_by_user',
+        )
+        read_only_fields = fields
+
+    def get_is_liked_by_user(self, obj: business.models.Promo) -> bool:
+        """
+        Checks whether the current user has liked this promo.
+        """
+        request = self.context.get('request')
+        if (
+            request
+            and hasattr(request, 'user')
+            and request.user.is_authenticated
+        ):
+            return user.models.PromoLike.objects.filter(
+                promo=obj,
+                user=request.user,
+            ).exists()
+        return False
+
+    def get_is_activated_by_user(self, obj: business.models.Promo) -> bool:
+        """
+        Checks whether the current user has activated this promo code.
+        """
+        request = self.context.get('request')
+
+        if not (
+            request
+            and hasattr(request, 'user')
+            and request.user.is_authenticated
+        ):
+            return False
+
+        return user.models.PromoActivationHistory.objects.filter(
+            promo=obj,
+            user=request.user,
+        ).exists()
+
+
+class BaseCommentSerializer(rest_framework.serializers.ModelSerializer):
+    """
+    Base serializer for promo comments.
+    """
+
+    text = rest_framework.serializers.CharField(
+        min_length=user.constants.COMMENT_TEXT_MIN_LENGTH,
+        max_length=user.constants.COMMENT_TEXT_MAX_LENGTH,
+    )
+
+    class Meta:
+        model = user.models.PromoComment
+        fields = ('text',)