kasmVNC: support kasm official images

[bpmct]

https://kasmweb.com/docs/latest/guide/custom_images.html

This is what happened when I tried to start my workspace with kasmweb/postman:1.16.0:

�[0;1mLogging into Coder...

�[0;1mInstalling filebrowser 

⚙️ Creating settings file...
�[0;1mInstalling code-server!
Detected Distribution: ubuntu
Detected Version: 20.04
Detected Architecture: x86_64
vncserver is already installed.
vncserver already installed. Skipping installation.
sudo: a terminal is required to read the password; either use the -S option to read from standard input or configure an askpass helper
🚀 Starting KasmVNC server...
Attempting to authenticate with flag URL: 'https://dev.coder.com'
  Welcome to Coder, bpmct! You're authenticated.
Downloading File Browser for linux/amd64...
https://github.com/filebrowser/filebrowser/releases/download/v2.31.2/linux-amd64-filebrowser.tar.gz
Extracting...
Putting filemanager in /usr/local/bin (may require password)
sudo: a terminal is required to read the password; either use the -S option to read from standard input or configure an askpass helper
Aborted, error 1 in command: $sudo_cmd mv "$PREFIX/tmp/$filemanager_bin" "$install_path/$filemanager_bin"
🥳 Installation complete! 

👷 Starting filebrowser in background... 

📂 Serving /home/kasm-user at http://localhost:13339 

Running 'filebrowser --noauth --root /home/kasm-user --port 13339' 

📝 Logs at /tmp/filebrowser.log 

#=#=#                                                                         

                                                                           0.0%
#                                                                          2.4%
#############                                                             19.1%
##########################                                                37.3%
#######################################                                   54.8%
###################################################                       72.1%
################################################################          89.4%
######################################################################## 100.0%
🥳 code-server has been installed in /tmp/code-server

jq is required to install extensions from a workspace file.
🥳 code-server has been installed in /tmp/code-server

jq is required to install extensions from a workspace file.

[matifali]

Kasm images contain preconfigured SSL settings that conflict with our module not using SSL.
I was able to support them by overwriting the kasmvnc.yaml config as,

FROM kasmweb/postman:1.16.0
ARG USER=kasm-user
USER root
# Overwrite the existing config file to disable SSL
RUN cat <<EOF > /etc/kasmvnc/kasmvnc.yaml
network:
  protocol: http
  ssl:
    require_ssl: false
  udp:
    public_ip: 127.0.0.1
EOF
RUN addgroup $USER ssl-cert
USER $USER

What do you think about it @bpmct?