release: stable-5142-1

* b0cb4a18 web: update TLS config to Mozilla security guidelines
* 06012127 web: replace certbot with acme.sh
* 43f678d9 build: refactor Makefile
* b00f92ae web: use Python 3 only for certbot
* 880b9b0e core: update base image to Debian Buster
* ba011900 web: prevent s6 from restarting cron if it shouldn't be run
* 42a43462 etherpad: use official image and making skin full width
* c36c4d02 web: always rebuild nginx configs on start
* aea4411d Adds private server.
* 6b69576c web: add ability to configure tokenAuthUrl
* ff6d9bc6 Fix websocket
* e5746ae0 misc: add ENABLE_PREJOIN_PAGE to .env
* 465816b4 web,prosody: turn on XMPP WebSocket by default
* d747bfbe web,prosody: add XMPP WebSocket / Stream Management support
* 130eb551 jvb: migrate to new config file
* 52904994 doc: updated link for running behind NAT
* 7cb470c3 misc: support/encourage usage of ShellCheck
* 04a210f5 misc: working on latest