* provider/datadog 9869: Validate credentials when initialising client.
* provider/datadog Pull in new version of go-datadog-api.
* provider/datadog Update testAccCheckDatadogMonitorConfigNoThresholds test config.
- Don't drop wildcard if it's the only one.
- Remove monitor resource, it's been replaced by metric_alert,
outlier_alert and service_check
- Refactor to be closer to the API; each resource creates exactly *one*
resource, not 2, this removes much unneeded complexity. A warning
threshold is now supported by the API.
- Remove fuzzy resources like graph, and resources that used them for
dashboard and screenboards. I'd welcome these resources, but the
current state of Terraform and the Datadog API does not allow these to
be implemented in a clean way.
- Support multiple thresholds for metric alerts, remove notify argument.