feat(billing): add missing payment methods and configurations

- Added migration to include global payment method configurations for Stripe and PayPal (both disabled).
- Ensured existing payment methods like bank transfer and manual payment are correctly configured.
- Added database constraints and indexes for improved data integrity in billing models.
- Introduced foreign key relationship between CreditTransaction and Payment models.
- Added webhook configuration fields to PaymentMethodConfig for future payment gateway integrations.
- Updated SignUpFormUnified component to handle payment method selection based on user country and plan.
- Implemented PaymentHistory component to display user's payment history with status indicators.

backend/igny8_core/modules/billing/serializers.py

@@ -1,6 +1,8 @@
 """
 Serializers for Billing Models
 """
+from typing import Any, Dict, Optional
+from decimal import Decimal
 from rest_framework import serializers
 from .models import CreditTransaction, CreditUsageLog
 from igny8_core.auth.models import Account
@@ -8,7 +10,11 @@ from igny8_core.business.billing.models import PaymentMethodConfig, Payment
 
 
 class CreditTransactionSerializer(serializers.ModelSerializer):
-    transaction_type_display = serializers.CharField(source='get_transaction_type_display', read_only=True)
+    """Serializer for credit transactions"""
+    transaction_type_display: serializers.CharField = serializers.CharField(
+        source='get_transaction_type_display', 
+        read_only=True
+    )
     
     class Meta:
         model = CreditTransaction
@@ -20,7 +26,11 @@ class CreditTransactionSerializer(serializers.ModelSerializer):
 
 
 class CreditUsageLogSerializer(serializers.ModelSerializer):
-    operation_type_display = serializers.CharField(source='get_operation_type_display', read_only=True)
+    """Serializer for credit usage logs"""
+    operation_type_display: serializers.CharField = serializers.CharField(
+        source='get_operation_type_display', 
+        read_only=True
+    )
     
     class Meta:
         model = CreditUsageLog
@@ -34,24 +44,27 @@ class CreditUsageLogSerializer(serializers.ModelSerializer):
 
 class CreditBalanceSerializer(serializers.Serializer):
     """Serializer for credit balance response"""
-    credits = serializers.IntegerField()
-    plan_credits_per_month = serializers.IntegerField()
-    credits_used_this_month = serializers.IntegerField()
-    credits_remaining = serializers.IntegerField()
+    credits: serializers.IntegerField = serializers.IntegerField()
+    plan_credits_per_month: serializers.IntegerField = serializers.IntegerField()
+    credits_used_this_month: serializers.IntegerField = serializers.IntegerField()
+    credits_remaining: serializers.IntegerField = serializers.IntegerField()
 
 
 class UsageSummarySerializer(serializers.Serializer):
     """Serializer for usage summary response"""
-    period = serializers.DictField()
-    total_credits_used = serializers.IntegerField()
-    total_cost_usd = serializers.DecimalField(max_digits=10, decimal_places=2)
-    by_operation = serializers.DictField()
-    by_model = serializers.DictField()
+    period: serializers.DictField = serializers.DictField()
+    total_credits_used: serializers.IntegerField = serializers.IntegerField()
+    total_cost_usd: serializers.DecimalField = serializers.DecimalField(max_digits=10, decimal_places=2)
+    by_operation: serializers.DictField = serializers.DictField()
+    by_model: serializers.DictField = serializers.DictField()
 
 
 class PaymentMethodConfigSerializer(serializers.ModelSerializer):
     """Serializer for payment method configuration"""
-    payment_method_display = serializers.CharField(source='get_payment_method_display', read_only=True)
+    payment_method_display: serializers.CharField = serializers.CharField(
+        source='get_payment_method_display', 
+        read_only=True
+    )
     
     class Meta:
         model = PaymentMethodConfig
@@ -66,43 +79,66 @@ class PaymentMethodConfigSerializer(serializers.ModelSerializer):
 
 class PaymentConfirmationSerializer(serializers.Serializer):
     """Serializer for manual payment confirmation"""
-    invoice_id = serializers.IntegerField(required=True)
-    payment_method = serializers.ChoiceField(
+    invoice_id: serializers.IntegerField = serializers.IntegerField(required=True)
+    payment_method: serializers.ChoiceField = serializers.ChoiceField(
         choices=['bank_transfer', 'local_wallet'],
         required=True
     )
-    manual_reference = serializers.CharField(
+    manual_reference: serializers.CharField = serializers.CharField(
         required=True,
         max_length=255,
         help_text="Transaction reference number"
     )
-    manual_notes = serializers.CharField(
+    manual_notes: serializers.CharField = serializers.CharField(
         required=False,
         allow_blank=True,
         help_text="Additional notes about the payment"
     )
-    amount = serializers.DecimalField(
+    amount: serializers.DecimalField = serializers.DecimalField(
         max_digits=10,
         decimal_places=2,
         required=True
     )
-    proof_url = serializers.URLField(
+    proof_url: serializers.URLField = serializers.URLField(
         required=False,
         allow_blank=True,
         help_text="URL to receipt/proof of payment"
     )
+    
+    def validate_proof_url(self, value: Optional[str]) -> Optional[str]:
+        """Validate proof_url is a valid URL format"""
+        if value and not value.strip():
+            raise serializers.ValidationError("Proof URL cannot be empty if provided")
+        if value:
+            # Additional validation: must be http or https
+            if not value.startswith(('http://', 'https://')):
+                raise serializers.ValidationError("Proof URL must start with http:// or https://")
+        return value
+    
+    def validate_amount(self, value: Optional[Decimal]) -> Decimal:
+        """Validate amount has max 2 decimal places"""
+        if value is None:
+            raise serializers.ValidationError("Amount is required")
+        if value <= 0:
+            raise serializers.ValidationError("Amount must be greater than 0")
+        # Check decimal precision (max 2 decimal places)
+        if value.as_tuple().exponent < -2:
+            raise serializers.ValidationError("Amount can have maximum 2 decimal places")
+        return value
+
+
 class LimitCardSerializer(serializers.Serializer):
     """Serializer for individual limit card"""
-    title = serializers.CharField()
-    limit = serializers.IntegerField()
-    used = serializers.IntegerField()
-    available = serializers.IntegerField()
-    unit = serializers.CharField()
-    category = serializers.CharField()
-    percentage = serializers.FloatField()
+    title: serializers.CharField = serializers.CharField()
+    limit: serializers.IntegerField = serializers.IntegerField()
+    used: serializers.IntegerField = serializers.IntegerField()
+    available: serializers.IntegerField = serializers.IntegerField()
+    unit: serializers.CharField = serializers.CharField()
+    category: serializers.CharField = serializers.CharField()
+    percentage: serializers.FloatField = serializers.FloatField()
 
 
 class UsageLimitsSerializer(serializers.Serializer):
     """Serializer for usage limits response"""
-    limits = LimitCardSerializer(many=True)
+    limits: LimitCardSerializer = LimitCardSerializer(many=True)