[#83] Allow member_role to be configurable

Signed-off-by: crynobone <crynobone@gmail.com>
[#83] Rename member_role key

Signed-off-by: crynobone <crynobone@gmail.com>
Add remove user functional test when user has multiple roles

Signed-off-by: crynobone <crynobone@gmail.com>