https://gitlab.com/gitlab-org/gitlab-ce/issues/62971
Adds support to EnvironmentsController#metrics_dashboard
for the following params: group, title, y_label
These params are used to uniquely identify a panel on
the metrics dashboard.
Metrics are stored in several places, so this adds
utilities to find a specific panel from the database
or filesystem depending on the metric specified.
Also moves some shared utilities into separate classes,
notably default values and errors.
Correct the ordering of metrics on performance dashboard. Before common
metrics were moved into the DB, metric groups were ordered by the
priority defined in the common_metrics.yml file.
This commit adds a priority to each metric group in the PrometheusMetric
model.
It also combines title, priority and required_metrics into one frozen
GROUP_DETAILS hash so that the code is clearer.
This can be done since there is a fixed set of groups which are not
configurable.
