time: remove timezone out of api
currently api of time API of foris-controller contains a field called:
timezone which is mapped to openwrt uci confing
system.@system.timezone which is a bit ugly string. e.g.
CET-1CEST,M3.5.0,M10.5.0/3 for czech timezone.
Basically this information is redundant, because the call already contains
city. And the ugly string could be derived from these data in backend.
To this task is about moving this logic from front-end to backend.
The new call should not contain
timezone field, but the
system.@system.timezone should be updated according to
see https://openwrt.org/docs/guide-user/base-system/system_configuration for timezone field format.