post https://api.mixmax.com/v1/contactgroups//contacts
Adds a Contact to a Contact Group. You must own the group to add contacts to it.
Deprecated
This endpoint is now marked for deprecation. While this endpoint is still functional, it will be phased out in the future and should not be used in new development efforts.
You must either own or have edit access to the group to use this.
For response format, see /contacts API.