Slug validation does not consider namespaces

[anehx]

Currently, it's possible to create slugs on forms or questions etc. that are longer than they should be. This happens when ember-caluma was namespaced. If you create a slug that is e.g 2 chars less than the limit and you have a namespace of "123" it will be 2 chars longer than the actual maximum ("123-..."). Creating it will work, however, this object can't ever be edited again.

[anehx]

Should be done for options as well, but with the question slug (including namespace) as prefix