Added metrics metadata

dbrepo-dashboard-service/dashboards/system.json

...ice/src/main/java/at/tuwien/endpoints/SubsetEndpoint.java

...vice/src/main/java/at/tuwien/endpoints/TableEndpoint.java

...rvice/src/main/java/at/tuwien/endpoints/ViewEndpoint.java

...a-service/rest-service/src/main/resources/application.yml

...ervices/src/main/java/at/tuwien/config/MetricsConfig.java

...main/java/at/tuwien/gateway/impl/KeycloakGatewayImpl.java

...rvices/src/main/java/at/tuwien/mapper/MetadataMapper.java

...vices/src/main/java/at/tuwien/service/MetricsService.java

.../at/tuwien/service/impl/MetricsServicePrometheusImpl.java

dbrepo-ui/components/subset/SubsetList.vue

dbrepo-ui/components/view/ViewList.vue

dbrepo-ui/components/view/ViewToolbar.vue

...o-ui/pages/database/[database_id]/view/[view_id]/data.vue