My understanding is that Webex groups represent collections of Webex users: https://developer.webex.com/docs/api/v1/groups
You can retrieve the list of user Id's associated with a specific group via that resource, e.g.: GET https://webexapis.com/v1/groups/{groupId}/members
If by 'Webex end point' you are referring to Webex room/desk meeting devices (e.g. Room Kit), those can be configured in 'personal mode' (assigned to a Webex user) or 'workspace mode' (assigned to a workspace.) Devices in workspace mode are not associated to users, and so I'm not sure you can map groups->workspace endpoints. You can get a list of personal mode devices associated to a specific user via: GET https://webexapis.com/v1/devices?personId={personId}
Can you elaborate on the requirement to send messages to Webex rooms? Are these Webex spaces/rooms, or conference rooms (with Webex meeting endpoints in them?) If the former, do you want to send a message to every Webex space where every Webex user in a group is a member, or..?
