fix enroll and reenroll relationship

enrollments-events/app/enrollment.py

@@ -1,4 +1,7 @@
+from abc import ABC
+from dataclasses import dataclass
 from datetime import timedelta
+from enum import Enum
 from typing import NotRequired, Self, TypedDict
 
 from layercake.dateutils import now, ttl
@@ -32,15 +35,16 @@ Subscription = TypedDict(
 )
 
 
-class LinkedEntity(str):
-    def __new__(cls, id: str, type: str) -> Self:
-        return super().__new__(cls, '#'.join([type.lower(), id]))
+class Kind(str, Enum):
+    ORDER = 'ORDER'
+    ENROLLMENT = 'ENROLLMENT'
 
-    def __init__(self, id: str, type: str) -> None:
-        # __init__ is used to store the parameters for later reference.
-        # For immutable types like str, __init__ cannot change the instance's value.
-        self.id = id
-        self.type = type
+
+@dataclass(frozen=True)
+class LinkedEntity(ABC):
+    id: str
+    kind: Kind
+    table_name: str | None = None
 
 
 class DeduplicationConflictError(Exception):
@@ -76,29 +80,27 @@ def enroll(
         )
 
         # Relationships between this enrollment and its related entities
-        for parent_entity in linked_entities:
-            perent_id = parent_entity.id
-            entity_sk = f'LINKED_ENTITIES#{parent_entity.type}'
-            keyprefix = parent_entity.type.lower()
-
+        for entity in linked_entities:
             # Parent knows the child
             transact.put(
                 item={
-                    'id': perent_id,
-                    'sk': f'{entity_sk}#CHILD',
+                    'id': entity.id,
+                    'sk': f'LINKED_ENTITIES#{entity.kind.value}#CHILD',
                     'created_at': now_,
-                    f'{keyprefix}_id': enrollment.id,
+                    'enrollment_id': enrollment.id,
                 },
                 cond_expr='attribute_not_exists(sk)',
+                table_name=entity.table_name,
             )
 
+            keyprefix = entity.kind.value.lower()
             # Child knows the parent
             transact.put(
                 item={
                     'id': enrollment.id,
-                    'sk': f'{entity_sk}#PARENT',
+                    'sk': f'LINKED_ENTITIES#{entity.kind.value}#PARENT',
                     'created_at': now_,
-                    f'{keyprefix}_id': perent_id,
+                    f'{keyprefix}_id': entity.id,
                 },
                 cond_expr='attribute_not_exists(sk)',
             )