Updates the EnvironmentController#metrics_dashboard endpoint to support a "dashboard" param, which can be used to specify the filepath of a dashboard configuration from a project repository. Dashboard configurations are expected to be stored in .gitlab/dashboards/. Updates dashboard post-processing steps to exclude custom metrics, which should only display on the system dashboard.  | 
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| .. | ||
| finder_spec.rb | ||
| processor_spec.rb | ||
| project_dashboard_service_spec.rb | ||
| system_dashboard_service_spec.rb | ||