api: add a template 'varlist' entrypoint

restapi/embedded_spec.go

restapi/operations/logging.go

restapi/operations/prometheus.go

restapi/operations/rednerd_api.go

restapi/operations/template_management/template_varlist.go

...ations/template_management/template_varlist_parameters.go

...ations/template_management/template_varlist_prometheus.go

...rations/template_management/template_varlist_responses.go

...ations/template_management/template_varlist_urlbuilder.go

restapi/operations/user_management/user_apikey_add.go

restapi/operations/user_management/user_apikey_delete.go

restapi/operations/user_management/user_apikey_list.go

swagger.yaml