* Alerting: Repurpose rule testing endpoint to return potential alerts
This feature replaces the existing no-longer in-use grafana ruler testing API endpoint /api/v1/rule/test/grafana. The new endpoint returns a list of potential alerts created by the given alert rule, including built-in + interpolated labels and annotations.
The key priority of this endpoint is that it is intended to be as true as possible to what would be generated by the ruler except that the resulting alerts are not filtered to only Resolved / Firing and ready to be sent.
This means that the endpoint will, among other things:
- Attach static annotations and labels from the rule configuration to the alert instances.
- Attach dynamic annotations from the datasource to the alert instances.
- Attach built-in labels and annotations created by the Grafana Ruler (such as alertname and grafana_folder) to the alert instances.
- Interpolate templated annotations / labels and accept allowed template functions.
* Implement backtesting engine that can process regular rule specification (with queries to datasource) as well as special kind of rules that have data frame instead of query.
* declare a new API endpoint and model
* add feature toggle `alertingBacktesting`
This changes the API codegen template (controller-api.mustache) to simplify some names. When this package was created, most APIs "forked" to either a Grafana backend implementation or a "Lotex" remote implementation. As we have added APIs it's no longer the case. Provisioning, configuration, and testing APIs do not fork, and we are likely to add additional APIs that don't fork.
This change replaces {{classname}}ForkingService with {{classname}} for interface names, and names the concrete implementation {{classname}}Handler. It changes the implied implementation of a route handler from fork{{nickname}} to handle{{nickname}}. So PrometheusApiForkingService becomes PrometheusApi, ForkedPrometheusApi becomes PrometheusApiHandler and forkRouteGetGrafanaAlertStatuses becomes handleRouteGetGrafanaAlertStatuses
It also renames some files - APIs that do no forking go from forked_{{name}}.go to {{name}}.go and APIs that still fork go from forked_{{name}}.go to forking_{{name}}.go to capture the idea that those files a "doing forking" rather than "are a fork of something."
Signed-off-by: Joe Blubaugh <joe.blubaugh@grafana.com>
