feat(time_entries): add time_entries app's basic structure and endpoints

apps/time_entries/services/rates.py

@@ -0,0 +1,22 @@
+from apps.projects.models import ProjectRate, ProjectUserRate
+
+
+def resolve_rate(user, project):
+    user_rate = ProjectUserRate.objects.filter(
+        user=user,
+        project=project,
+        is_active=True,
+    ).order_by("-effective_from").first()
+
+    if user_rate:
+        return user_rate.hourly_rate, user_rate.currency
+
+    project_rate = ProjectRate.objects.filter(
+        project=project,
+        is_active=True,
+    ).order_by("-effective_from").first()
+
+    if project_rate:
+        return project_rate.hourly_rate, project_rate.currency
+
+    return None, "USD"