USE AT YOUR OWN RISK!  I ACCEPT NO RESPONSIBILITY FOR YOUR LACK OF RESPONSIBILITY!  Make backups, or better yet, don't use this!  I can confidently say it works for me, but I have no idea if it'll work for you.  You have been warned.

Git clone https://sources.gtsvr.net/edschuy95/yeastar-voipms-webhook-proxy.git

For docker or bare OS
copy .env.template.py to .env and edit

Docker/compose
docker-compose up -d --build 

Bare OS
pip install requirements or apt install components (requirements.txt)
launch app with gunicorn
prepare as a systemd service (todo: add template or helper script)

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Yeastar stuff: 

In the API key section for the SMS channel, enter your voip.ms API credentials separated by ||| like so:

api_username|||api_password

Voip.ms stuff:

Just point voip.ms DIDS to the /{ENDPOINT_OBSCURITY}/voipms-inbound endpoint.