Horay!
I finally deployed first version of my GADM api service. It is very rough at the moment. The deployment process is semi-automated. I can initialize new ubuntu VM, launch dockerized server and database, ingest GADM geopackage and run migrations with just few manual interventions.
Some bash script that I wrote will help me to automate the process even further with github CI/CD pipeline.
At the moment I am happy I can ping my server from local machine and confirm that pagination and filtering works as intended for all GADM levels!