http://eweiibe6tdjsdprb4px6rqrzzcsi22m4koia44kc5pcjr7nec2rlxyad.onion/help/administration/integration/plantuml.md
Your server must catch external PlantUML
calls to https://gitlab.example.com/-/plantuml/ and redirect them to the
local PlantUML server. Depending on your setup, the URL is either of the
following:
http://plantuml:8080/
http://localhost:8080/plantuml/
http://plantuml:8005/
http://localhost:8005/plantuml/
If you're running GitLab with TLS
you must configure this redirection, because PlantUML uses the insecure HTTP protocol.