Adoc export

[dragonchaser]

This PR adds support for generating adoc files for the environment variables for consumption in the docs.
Version information is still missing (but prepared) and needs to be annotated with the variables and output needs to be added to the template.

/cc @mmattel

Refs #3583

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[ownclouders]

💥 Acceptance test Core-API-Tests-ocis-storage-2 failed. Further test are cancelled...

[mmattel]

I would add the version field as it was in the original - even it will not get populated automatically atm (no generation code, no field in the go code), but it will force us to make this happen as the field is visible...
You may also, for the time being, add a default value like +1.20.0 (or whatever the beta version will be) as done in the original adoc file.

[butonic]

@dragonchaser how can I test this?

[dragonchaser]

@butonic

goto docs/helpers
run: go run configextractor.go

[dragonchaser]

I would add the version field as it was in the original - even it will not get populated automatically atm (no generation code, no field in the go code), but it will force us to make this happen as the field is visible... You may also, for the time being, add a default value like +1.20.0 (or whatever the beta version will be) as done in the original adoc file.

this is already prepared, just not output in the template to avoid confusion

[mmattel]

LGTM