feat(backend): consolidate queue logic for scheduling

backend/database/models/serviceavailability.py

@@ -0,0 +1,9 @@
+from dataclasses import dataclass
+from ._base import BaseModel
+
+
+@dataclass()
+class ServiceAvailability(BaseModel):
+    ServiceAvailabilityId: int
+    MemberId: int
+    ServiceTypeId: int