[feature] Support for environmental substitution in config.json

[arulrajnet]

This PR has

• support for environmental substitution in config.json using python Template. Refer comment in File/environment-based secrets #35
• Allow to run the scripts from root/any folder. For ex ./scripts/docker-build.sh

[arulrajnet]

@timothymiller tested the same in my setup
https://github.com/arulrajnet/tamilillam.arulraj.net/blob/main/docker-compose.yml
https://github.com/arulrajnet/tamilillam.arulraj.net/blob/main/conf/ddns/config.json

[arulrajnet]

@timothymiller Is there anything I am missing to merge this PR?

[arulrajnet]

@timothymiller do you actively maintain this project?

Seems no PR merged after Aug 2022

[andrp92]

👀

[timothymiller]

┻━┻︵ (°□°)/ ︵ ┻━┻
Merging PRs tomorrow

[timothymiller]

Very cool @arulrajnet! Can you update this PR so the feature works as an either or.

Example: If environment variables are defined, then skip parsing config.json

I'd like to keep backwards compatibility for users of the existing config.json method.

[timothymiller]

I merged a few other PRs, one that added support for extracting IP from the network interface, instead of an HTTP request to Cloudflare. Would you mind syncing up with the master branch?

[arulrajnet]

@timothymiller Addressed all the comments.

• skip parsing config.json if the environment variables are defined
• Sync with master.

[arulrajnet]

@timothymiller could you review again?

[yorickdowne]

This is a pretty big deal for me, this'd allow me to not bind-mount config.json, and instead do all config via env variables.

A second PR could have a default config.json that can be overridden via bind mount.

[shaunbharat]

This is a pretty big deal for me, this'd allow me to not bind-mount config.json, and instead do all config via env variables.

A second PR could have a default config.json that can be overridden via bind mount.

Environment variables would also simplify things in my situation.

@timothymiller, I wanted to bring your attention back to this PR because it would be beneficial to my current home lab configuration. Is there any update on if/when this PR can be merged? Thanks!