Hello,
Here is the wiki page: bicycle=optional%20sidepath?uselang=en
However, your comment prompted me to check Oregon law and bicycle=use_sidepath is probably the appropriate tag. (https://oregon.public.law/statutes/ors_814.420#1-except-as-provided-in-subsections-2-and-3-of-this-section-a-p)

My source was the City of West Linn's Roadway Functional Classifications map. Which can be found as a layer here: https://geo.westlinnoregon.gov/Html5Viewer/index.html?viewer=Public