Show Better Validation Errors in SSH Keys Add

If someone tries to add a name with `Spaces and (Parens)` they'll be blocked from saving the form, but not given validation feedback in any way. Lame.

Start at the SSH Keys Add form and reproduce the problem by entering a name containing spaces and parentheses. Trace the validation handling for that field; done means the form still blocks the invalid submission and shows clear feedback explaining what needs to change.

Written by the indexing model from the issue text.