put https://api.productboard.com/feature-release-assignments/assignment
Assigns a feature into a release or removes a feature from a release depending on the assigned parameter.
Take into account that it's possible to achieve use cases that are not possible in the UI. For example you can assign subfeature into a release without its parent feature, but then you won't see it on a roadmap. If needed, assign the parent feature into the release. Subfeatures without a parent feature are not supported on a roadmap right now and might never be.