add a sorted_clins property for clin sorting logic

CLINS have a special ordering:
 - First, they are sorted by the last three digits
 - Then, they are sorted by the first digit

Trying to add CLIN sorting logic to the relationship field in the task
order proved to be more challenging than expected. So, a separate
property was defined in order to access the clins in sorted order.

atst/models/clin.py

@@ -38,7 +38,7 @@ class CLIN(Base, mixins.TimestampsMixin):
     @property
     def type(self):
         return "Base" if self.number[0] == "0" else "Option"
-    
+
     @property
     def is_completed(self):
         return all(

atst/models/task_order.py

@@ -47,6 +47,10 @@ class TaskOrder(Base, mixins.TimestampsMixin):
         "CLIN", back_populates="task_order", cascade="all, delete-orphan"
     )
 
+    @property
+    def sorted_clins(self):
+        return sorted(self.clins, key=lambda clin: (clin.number[1:], clin.number[0]))
+
     @hybrid_property
     def pdf(self):
         return self._pdf