Add .env file configuration to documentation

[marc-farre]

I think we should mention the new .env file in:

• https://docs.humhub.org/docs/admin/advanced-configuration
• https://docs.humhub.org/docs/admin/updating#upgrade-manually -> Restore individual files

[luke-]

@Semir1212 @mbumpalumpa Can you take care of it?

[Semir1212]

@marc-farre I am having difficulties understanding the topic. Could you please write a few lines for the documentation so that we don't get it wrong?

[marc-farre]

@Semir1212 it's about the new .env file: https://github.com/humhub/humhub/blob/develop/.env.example
The idea is to update the doc about the configuration file, because since 1.17:

• part of the configuration settings are done in this new file instead of protected/config/common.php
• upgrading HH manually requires keeping this file alongside with the .htaccess.

But I'm seeing that there is already a similar issue: https://github.com/humhub/humhub-internal/issues/437

And an open PR where most of the work is already done: https://github.com/humhub/documentation/pull/143/files

However, the 2 mentioned pages are not included in this PR:
https://docs.humhub.org/docs/admin/advanced-configuration
https://docs.humhub.org/docs/admin/updating#upgrade-manually -> Restore individual files

[Semir1212]

@marc-farre Thank you, could you please look into the PR and add the missing parts?

[luke-]

@gevorgmansuryan Can you please help here?