feat(backend): refactor mono repository

backend/models/enums.py

@@ -0,0 +1,42 @@
+# ------------------------------------------------------------
+# Centralised enumeration definitions for the data‑model layer.
+# Keeping them in one module avoids circular imports and makes
+# type‑checking / IDE completion straightforward.
+# ------------------------------------------------------------
+
+from __future__ import annotations
+
+from enum import StrEnum
+from typing import Any, Iterable
+
+
+class ScheduleStatus(StrEnum):
+    """
+    Canonical status values for a ``Schedule`` row.
+
+    Using ``StrEnum`` means the enum members behave like regular strings
+    (e.g. they can be written directly to SQLite) while still giving us
+    the safety and autocomplete of an enum.
+    """
+    PENDING   = "pending"
+    ACCEPTED  = "accepted"
+    DECLINED  = "declined"
+
+    @classmethod
+    def from_raw(cls, value: Any) -> "ScheduleStatus":
+        """
+        Convert an arbitrary value (often a plain string coming from the DB)
+        into a ``ScheduleStatus`` member.
+
+        Raises
+        ------
+        ValueError
+            If the value does not correspond to any defined member.
+        """
+        if isinstance(value, cls):
+            return value
+        try:
+            # ``cls(value)`` works because ``StrEnum`` subclasses ``str``.
+            return cls(value)
+        except ValueError as exc:
+            raise ValueError(f"Invalid ScheduleStatus: {value!r}") from exc