refactor: cleanup duplicate code (#36173)

api/fields/message_fields.py

@@ -9,6 +9,7 @@ from core.entities.execution_extra_content import ExecutionExtraContentDomainMod
 from fields.base import ResponseModel
 from fields.conversation_fields import AgentThought, JSONValue, MessageFile
 from graphon.file import File
+from libs.helper import to_timestamp
 
 type JSONValueType = JSONValue
 
@@ -39,9 +40,7 @@ class RetrieverResource(ResponseModel):
     @field_validator("created_at", mode="before")
     @classmethod
     def _normalize_created_at(cls, value: datetime | int | None) -> int | None:
-        if isinstance(value, datetime):
-            return to_timestamp(value)
-        return value
+        return to_timestamp(value)
 
 
 class MessageListItem(ResponseModel):
@@ -68,9 +67,7 @@ class MessageListItem(ResponseModel):
     @field_validator("created_at", mode="before")
     @classmethod
     def _normalize_created_at(cls, value: datetime | int | None) -> int | None:
-        if isinstance(value, datetime):
-            return to_timestamp(value)
-        return value
+        return to_timestamp(value)
 
 
 class WebMessageListItem(MessageListItem):
@@ -106,9 +103,7 @@ class SavedMessageItem(ResponseModel):
     @field_validator("created_at", mode="before")
     @classmethod
     def _normalize_created_at(cls, value: datetime | int | None) -> int | None:
-        if isinstance(value, datetime):
-            return to_timestamp(value)
-        return value
+        return to_timestamp(value)
 
 
 class SavedMessageInfiniteScrollPagination(ResponseModel):
@@ -121,12 +116,6 @@ class SuggestedQuestionsResponse(ResponseModel):
     data: list[str]
 
 
-def to_timestamp(value: datetime | None) -> int | None:
-    if value is None:
-        return None
-    return int(value.timestamp())
-
-
 def format_files_contained(value: JSONValueType) -> JSONValueType:
     if isinstance(value, File):
         # Response payloads must preserve legacy file keys like `related_id`/`url`