[RENDERER]: add optionalAttribute / spread tests when values are regular expressions

[quarkus]

Find out if it actually makes sense to render complex expressions like:
/[a-z0-9!#$%&'+/=?^_{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_{|}~-]+)@(?:a-z0-9?.)+a-z0-9?/g

If so, write tests, fix bugs.

Would also be nice to find out how other places handle these values (attr assignment / reflection / parsing) handle these cases

[quarkus]

relation: #123 (comment)