Versioning by adding, and the field you can never rename

The cheapest API version is the one you never create, and that is achievable for longer than most teams expect if every change is additive.

SAFE          adding a field
              adding an optional parameter
              adding a new endpoint

BREAKING      renaming or removing a field
              changing a type: 4900 -> "4900"
              changing nullability of something a client dereferences
              tightening validation on an existing parameter
              changing an HTTP status for an existing condition

Tightening validation is the one that reads as a bug fix and is not: an endpoint that has accepted a null phone number for a year has clients that send one. The discipline is a checklist item in review rather than a principle, because principles lose to a tidy-up on a Friday. A field with a bad name stays badly named, and accepting that is the price of not maintaining two versions.