I gave to www.flussu.com, (our no-code, BPM, workflow software), the ability of read/write from a personal Google 📆 Calendar.
Then people can add to their workflows, a step or inner code that can set events for the user, checking for spare time before propose open dates.
As the whole product, the new ability is made as a microservice api that can operate inside, or on different machines than the one that runs that workflow.