feat(projects): add project-specific member rates

apps/projects/api/serializers.py

@@ -1,6 +1,9 @@
+from decimal import Decimal
+
 from rest_framework import serializers
 from core.serializers.base import BaseModelSerializer
 from apps.projects.models import Project
+from apps.workspaces.models import PriceUnit
 
 
 class ProjectSerializer(BaseModelSerializer):
@@ -54,3 +57,23 @@ class ProjectAccessMutationSerializer(serializers.Serializer):
         child=serializers.UUIDField(),
         allow_empty=False,
     )
+
+
+class ProjectAccessRateMutationSerializer(serializers.Serializer):
+    workspace = serializers.UUIDField()
+    user = serializers.UUIDField()
+    project = serializers.UUIDField()
+    hourly_rate = serializers.DecimalField(
+        max_digits=10,
+        decimal_places=2,
+        min_value=Decimal("0.01"),
+        required=False,
+        allow_null=True,
+    )
+    currency = serializers.CharField(max_length=3, required=False, default="USD")
+
+    def validate_currency(self, value):
+        code = value.upper()
+        if not PriceUnit.objects.filter(code=code, is_deleted=False).exists():
+            raise serializers.ValidationError("Selected price unit is invalid.")
+        return code