It is my opinion that the insertion of the character is the most flexible and the "correct" way to address this need, and indeed I teach the use of this character in my lecture on "breaks and keeps".

Another possiblity is to allow the user to augment the
processor's line breaking or hyphenation strategy. It's
"processor specific" anyway (and, to some degree, sadly).

As a famous example, you can supply patterns to a pattern
based hyphenator which will hyphenate an URL after each
slash and activate it by a pseudo-language setting "x-url"
or something. Don't forget to set the hyphenation character
to a ZWS too.