I avoided changing the pre-existing extraroute implementation to
also avoid any breakage of legacy behavior. Alternatively we can
refactor the extraroute code to better fit both APIs:
* the old: updates to the 'routes' attribute and
* the new: actions 'add_extraroutes' / 'remove_extraroutes'.
Change-Id: Ia78e0e02de4a42a056e3ff654d8b6976a4e52616
Closes-Bug: #1826396 (rfe)
Depends-On: https://review.opendev.org/679259
Related-Change: https://review.opendev.org/655680 (spec)