initial env var ingestion for rev proxy configs

[thelamer]

I have tested this pretty thoroughly at this point, it is bolt on logic so will not have an effect on any existing setups unless you can think of any possible reason someone would be passing an env var starting with "PROXY_CONFIG_" to a swag container.

The most basic string is incredibly useful to do subdomain setup to a port using a service name as :

- 'PROXY_CONFIG_WEBTOP={"port": 3000}'

This basically just works in most cases subdomain to a port, but all the options are there to get way more complex like in the case of Plex:

      PROXY_CONFIG_PLEX: '{"port":32400,"proxy_redirect_off":true,"buffering_off":true,"proxy_set_headers":[{"key":"X-Plex-Client-Identifier","value":"$http_x_plex_client_identifier"},{"key":"X-Plex-Device","value":"$http_x_plex_device"},{"key":"X-Plex-Device-Name","value":"$http_x_plex_device_name"},{"key":"X-Plex-Platform","value":"$http_x_plex_platform"},{"key":"X-Plex-Platform-Version","value":"$http_x_plex_platform_version"},{"key":"X-Plex-Product","value":"$http_x_plex_product"},{"key":"X-Plex-Token","value":"$http_x_plex_token"},{"key":"X-Plex-Version","value":"$http_x_plex_version"},{"key":"X-Plex-Nocache","value":"$http_x_plex_nocache"},{"key":"X-Plex-Provides","value":"$http_x_plex_provides"},{"key":"X-Plex-Device-Vendor","value":"$http_x_plex_device_vendor"},{"key":"X-Plex-Model","value":"$http_x_plex_model"}],"extra_locations":[{"path":"/library/streams/","custom_directives":["proxy_pass_request_headers off"]}]}'

The docced examples show the - array member syntax with escaped $ being double $$ and the whole thing being wrapped in single quotes but the object syntax like the plex example above is much more forgiving.

I think this is a good first step and maybe down the line we can look at using jinja templates for the ini generation and get everything in an env var format if possible.

[LinuxServer-CI]

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[thelamer]

Made the env tamplates directory a dedicated thing so it will not delete anyone's custom configs.

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