feat(pricing): add workspace user rates and price units

apps/workspaces/services/rates.py

@@ -0,0 +1,54 @@
+from django.utils import timezone
+
+from apps.workspaces.models import WorkspaceUserRate
+
+
+def upsert_workspace_user_rate(workspace, user_id, hourly_rate, currency="USD"):
+    currency = currency.upper()
+    rate = WorkspaceUserRate.objects.filter(
+        workspace=workspace,
+        user_id=user_id,
+        is_deleted=False,
+    ).first()
+
+    if rate:
+        update_fields = []
+        if rate.hourly_rate != hourly_rate:
+            rate.hourly_rate = hourly_rate
+            update_fields.append("hourly_rate")
+        if rate.currency != currency:
+            rate.currency = currency
+            update_fields.append("currency")
+        if not rate.is_active:
+            rate.is_active = True
+            update_fields.append("is_active")
+        if update_fields:
+            update_fields.append("updated_at")
+            rate.save(update_fields=update_fields)
+        return rate
+
+    return WorkspaceUserRate.objects.create(
+        workspace=workspace,
+        user_id=user_id,
+        hourly_rate=hourly_rate,
+        currency=currency,
+        effective_from=timezone.now(),
+        is_active=True,
+    )
+
+
+def update_workspace_user_rate(rate_instance, **kwargs):
+    if "currency" in kwargs and kwargs["currency"]:
+        kwargs["currency"] = kwargs["currency"].upper()
+
+    update_fields = []
+    for field, value in kwargs.items():
+        if hasattr(rate_instance, field) and getattr(rate_instance, field) != value:
+            setattr(rate_instance, field, value)
+            update_fields.append(field)
+
+    if update_fields:
+        update_fields.append("updated_at")
+        rate_instance.save(update_fields=update_fields)
+
+    return rate_instance