So the general policy statement here is that the FHIR2 module will support any resources for which there is an identified need and which can be populated using data from OpenMRS core. We also intend to provide a mechanism so that any OpenMRS module can provide new FHIR resources that are not a part of the the FHIR2 module and have those be made available through the FHIR2 module FHIR server. Modules can already override the default behaviour of any FHIR resources provided by the FHIR2 module. Eventually all of this will be documented on the OpenMRS Wiki.
From a pure FHIR perspective, the relevant resources for appointment scheduling are Appointment, Schedule, and Slot, depending on the data that the module needs to represent. The Appointment resource, in particular, has a number of details on the workflow for which it’s intended to be used. If this doesn’t meet the needs of the appointment module, we can always look into whether or not the Appointment resource, possibly with extensions, can be used to meet the use-case of the Bahmni appointment module. The Schedule and Slot resources I referred to above are primarily about representing a Practitioner or Practices schedule and can be used to tie appointments to schedules.