key of dns record metadata can not contain space

the dns record metadata key can not contain space, I want to confirm it's dedicated or not.

Saving a key containing space will still get success response, while it's actually not saved.

adding key containing space via portal, The page can show it added successfully, but after refreshing the page, we can see it's not saved

Start by locating the Azure DNS record metadata specification related to issue 8555 and inspect how metadata keys containing spaces are defined. Compare the specification with the reported portal behavior; done means the allowed key behavior is explicitly represented and the resulting API behavior is consistent with it.

Written by the indexing model from the issue text.