Scrape config labels in Loki config?

I’m looking to deploy Loki as an all-in-one microservice to start with and push logs from each service using the Logback appender plugin (long story, no permissions for daemonset, no access to fluentd, logs not accessible via promtail etc.). I want common labels with my prometheus metrics scrapes. Is it possible to add a scrape-config to loki where I can consistently add a set of labels to each ingested log?

(Apologies if this is in the docs - have been unable to find the right magic)