Adds an Icinga2 object to directly interface with InfluxDB's native HTTP API.
This supports optional basic authorization, and TLS transport. InfluxDB didn't
appear to like having the TLS stream kept open, so instead this object buffers
data points which are then flushed to InfluxDB as a batch write, either driven
by a configurable timeout or threshold.
As InfluxDB is a schema-less database the host and service templates are user
configurable allowing both the measurement field and tags to be set by the
end user via macro expansion. This allows access to tag fields from arbitrary
data associated with host.vars or service.vars. If a particular value is
unable to be resolved, the tag will be dropped and not transmitted to InfluxDB.
Also alters URL handling to omit array brackets when only a single value is
attached to a key, otherwise InfluxDB has a strop with non-standard syntax.
fixes#10480
Signed-off-by: Michael Friedrich <michael.friedrich@netways.de>
