feat(openapi): (Un)set role for user or group
feat(openapi): (Un)set role for user or group

* added definitions for set and unset role for single user or group
* this is needed for roles without complementary objects

CESNET/perun,zlamalp/perun,martin-kuba/perun,martin-kuba/perun,zlamalp/perun,CESNET/perun,martin-kuba/perun,zlamalp/perun,martin-kuba/perun,martin-kuba/perun,zlamalp/perun,CESNET/perun,zlamalp/perun,martin-kuba/perun,zlamalp/perun,CESNET/perun,CESNET/perun,CESNET/perun,CESNET/perun,zlamalp/perun,martin-kuba/perun