vmalert: support configuration file for notifiers
* vmalert notifiers now can be configured via file
see https://docs.victoriametrics.com/vmalert.html#notifier-configuration-file
* add support of Consul service discovery for notifiers config
see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1947
* add UI section for currently loaded/discovered notifiers
* deprecate `-rule.configCheckInterval` in favour of `-configCheckInterval`
* add ability to suppress logs for duplicated targets for notifiers discovery
* change behaviour of `vmalert_alerts_send_errors_total` - it now accounts
for failed alerts, not HTTP calls.
For a long time notifier.Addr flag was required. The assumption was that vmalert will
be always used for alerting. However, practice shows that some users need only
recording rules. In this case, requirement of notifier.Addr is ambigious.
The change verifies if loaded config contains recording or alerting rules and
if there are corresponding flags set. This is true for initial config load
and hot reload.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmalert: support multiple notifier urls (#584)
User now can set multiple notifier URLs in the same fashion
as for other vmutils (e.g. vmagent). The same is correct for
TLS setting for every configured URL. Alerts sending is done
in sequential way for respecting the specified URLs order.
* app/vmalert: add basicAuth support for notifier client (#585)
The change adds possibility to set basicAuth creds for notifier
client in the same fasion as for remote write/read and datasource.
The change adds no new functionality and aims to move flags definitions
to subpackages that are using them. This should improve readability
of the main function.
