It's a container that packages an nginx server with bindings for running Lua scripts and the Lua DKJSON library. When you have a project where you need to serve some application that needs access to the environment variables of the container then you can use this container to quickly do that.
The entrypoint script of the container checks the environment variables and expects to discover a special variable with the name NGINX_ENV_VARS. The value of this variable should be a comma-separated list contianing the names of all the environment variables that you want to have access to.
For example, if you want to load the variables ENV1=bla and ENV2=blabla to the environemnt of the container and make them accessible from the outside then you should set NGINX_ENV_VARS="ENV1,ENV2".
You do not need to do anything else, the entrypoint will take care of the rest during the container startup.
In your nginx configuration you must also include the following:
location /env {
content_by_lua_file /usr/local/openresty/nginx/lua/serve_vars.lua;
}
This /env endpoint is the one that you need to call with a GET request to get the json document with the environment variables that you have loaded to the container.