Handle the common case of one chunk when calculating the uncompressed size

Reference #992

data/database.py

@@ -784,6 +784,8 @@ class BlobUpload(BaseModel):
   sha_state = ResumableSHAField(null=True, default=resumablehashlib.sha256)
   location = ForeignKeyField(ImageStorageLocation)
   storage_metadata = JSONField(null=True, default={})
+  chunk_count = IntegerField(default=0)
+  uncompressed_byte_count = IntegerField(null=True)
 
   class Meta:
     database = db