I propose to allow the `-` char in allowed label characters
The reason is to allow to use more easily base64 ids, (like
https://github.com/dylang/shortid, ...), uuid's too in labels
`-` is also not used as a query operator as a plus
source:
https://doxygen.postgresql.org/ltree_8h.html#a1cb5d5dd0c364d720854e8a250967dd1