mesh-2433: add optional none type to upload chunk v1

Author: james-bradley-nhs

src/mesh_sandbox/views/outbox.py

@@ -26,8 +26,8 @@ class Config:
 
 
 class UploadChunkV1(BaseModel):
-    messageID: str = Field(default=None, description="message identifier, as supplied in the request url")  # type: ignore
-    blockID: int = Field(default=None, description="chunk number, as supplied in the request url")  # type: ignore
+    messageID: Union[str, None] = Field(default=None, description="message identifier, as supplied in the request url")  # type: ignore
+    blockID: Union[int, None] = Field(default=None, description="chunk number, as supplied in the request url")  # type: ignore
 
     class Config:
         title = "upload_chunk"