Zabbix

A......... [ZBX-21871] directed updates in usergroup.users to happen via user.usrgrps

* commit '0209da62990d4d65d63b0fe7eb6b77c3e1aae4ac':
  .......... [ZBX-21871] updated change-log
  .D........ [ZBX-21871] fixed ChangeLog entry
  .......... [ZBX-21871] fixed code style in API tests
  A......... [ZBX-21871] simplified and reverted code; updated change-log credits
  A......... [ZBX-21871] simplified and removed unnecessary code
  A......... [ZBX-21871] changed approach to passing user group updates; improved code style; updated change-log entry
  A......... [ZBX-21871] directed updates in usergroup.users to happen via user.usrgrps; updated test