PassFile in docker compose?

I'm trying to use docker compose to spin up postgres and pgAdmin services,
and the only sticking point is a minor one: I can't seem to get the
PassFile to work.

I wonder if it's not possible because of the following note at the bottom
this page of the pgAdmin docs
https://www.pgadmin.org/docs/pgadmin4/4.23/server_dialog.html:

```

Note

The password file option is only supported when pgAdmin is using libpq
v10.0 or later to connect to the server.
```
Tried:
- stackoverflowing
- most promising google result:
https://javaoraclesoa.blogspot.com/2020/01/pgadmin-in-docker-provisioning.html

Nothing seemed to work. Am I missing something? Or is it really just not
possible?

Thanks!
Z