Merge pull request coroot#521 from coroot/docs_authentication_sso_key…

…cloak

docs: add the `Authentication > SSO > Keycloak` section

Merge pull request coroot#518 from coroot/fix_517

fix panic in constructor (fixes coroot#517)

Merge pull request coroot#515 from coroot/metric_preaggregation

aggregate metrics in Prometheus queries

Merge pull request coroot#514 from coroot/constructor_less_kube_pod_m…

…etrics

constructor: reduce the number of `kube_pod` metrics

Merge pull request coroot#513 from coroot/prometheus_ooo

collector: respond with HTTP-200 to prevent agent retries on Prometheus HTTP-400

Merge pull request coroot#511 from coroot/constructor_annotations_cus…

…tom_applications

constructor: get `custom applications` from annotations

Merge pull request coroot#508 from coroot/recording_rules_for_dns_met…

…rics

aggregate per-container DNS metrics into per-app metrics

Merge pull request coroot#506 from coroot/internal_refactoring

Internal refactoring

Merge pull request coroot#505 from coroot/recording_rules

perf: aggregate instance-to-instance connections

Merge pull request coroot#503 from coroot/cache_log_prometheus_errors

cache: display and log prometheus query errors