Change the role of an existing workspace member.

• You must be an organization admin, a workspace admin, or hold a role with permission to edit member roles to call this endpoint.
• The role field accepts either a built-in role name (Admin, Manager, Member, Collaborator) or the name of a custom role defined for the workspace.
• The role of the workspace owner cannot be changed.
• The role of the last member with admin privileges in the workspace cannot be changed.
• When a member with a Guest license is promoted to any non-Collaborator role, the user's license is automatically upgraded to Full (Standard). If the organization has no free seats available, an additional seat is purchased.