No way to pass environment variables with query server config

As of CouchDB 2.3 the only way to configure query servers and their parameters is to use environment variables (see https://docs.couchdb.org/en/main/config/query-servers.html).
A common usage is to reconfigure maximum memory allocation for the javascript server by using: COUCHDB_QUERY_SERVER_JAVASCRIPT="/usr/bin/couchjs -S 536870912 /usr/share/server/main.js"
(as explained at: https://docs.couchdb.org/en/main/config/query-servers.html)

## Expected Behavior

There should be a way to pass environment variables while starting a snap service.

## Current Behavior

Currently there is no way to pass an environment variable to a snap application. Hence there is no way to reconfigure or add query servers.

## Possible Solution

An additional file in /var/snap/couchdb/9/etc/ that could hold the environment variables. It could be sourced upon startup.

## Your Environment

* Version used: 3.1.1, rev 9