feat: AUTO-3479 Add State enum

Closes AUTO-3479 @podosochnyy review

perxis/models.py

+import enum
+
 from dataclasses import dataclass
 
 
@@ -6,3 +8,10 @@ class Reference:
     id: str
     collection_id: str
     disabled: bool = False
+
+
+class State(str, enum.Enum):
+    DRAFT = "DRAFT"
+    PUBLISHED = "PUBLISHED"
+    CHANGED = "CHANGED"
+    ARCHIVED = "ARCHIVED"