link to https://semver.org/
MAJOR version when you make incompatible API changes: removing, renaming a field or adding a mandatory field. Changing the semantic of a field without renaming it should also be considered incompatible.
MINOR version when you add functionality in a backwards compatible manner: adding optional field
PATCH version when you make backwards compatible bug fixes.
Should a link to major version only (e.g. /api/1) redirects to the latest (e.g. /api.1.2.7) ?