What should be done:

• We need to prepare a Reference manual for PMM Server Docker Environment Variables.

• Link the documentation from related places including docker hub

Why:
There are no place for the user to know about env variables they can use

Benefit:
Less confusion and questions from the users

Details:

This can be a separate section in Documentation with the list of all Variables, their descriptions, and format + examples
Good example pmm1 way: https://www.percona.com/doc/percona-monitoring-and-management/1.x/glossary.option.html