KV should raise an error if the key contains unacceptable characters

[kevinhikaruevans]

Proposed change

If the key contains unacceptable characters (e.g. whitespace), an error should be raised. Maybe BadSubjectError can be reused or a new error can be created (e.g. BadKeyError).

It currently gives an UnexpectedEOF error and causes a TimeoutError. This is fairly confusing because it doesn't necessarily imply the key is bad and could be remedied by a quick check on the key.

Use case

I had somebody else feeding me some data, which was being fed into nats kv. I noticed that occasionally, an entry would cause an eof error and a timeout error and it wasn't very clear why. I finally realized that the user was putting spaces in the keys, which was causing problems in the underlying publish() call.

Contribution

Sure. I would assume it would be putting in a little check in put()