TT-RSS FreshAPI - fixing the docker-compose for a bind mount

Using the docker install of tt-rss I thought I'd give the freshRSS api (& gReader) a trial - gives more options for access via apps.
I'm using the standard docker compose, slightly edited to bind mount the plugins directory outside of the container so that it survives updates & so that I can copy plugins directly there.
Installation is easy enough

$ cd /bind/mount/location/tt-rss/plugins.local
$ git clone https://github.com/eric-pierce/freshapi.git

Then activate the plugin inside of tt-rss.
After that all you need is to use the server url
https://yourdomain.com/tt-rss/plugins.local/freshapi/api/greader.php

Or that's what is supposed to happen!

All that I got was a 404 from nginx 😦

To save you the hassle - if you open a shell in the nginx container you'll find that the plugins.local only shows the content of the tt-rss container's version. So the plugin can't be seen.
The fix is obvious, once you've figured that out - the default docker-compose mounts - app:/var/www/html:ro & we need to be able to "see" /bind/mount/location/tt-rss/plugins.local too
Add - bind/mount/location/ttrss/plugins.local:/var/www/html/tt-rss/plugins.local to the volumes in the nginx part of the docker-compose & restart & it works!