Fix NC warnings in settings

This is from https://files.staging.stackspin.net/settings/admin/overview, some of those might be related to the NC upgrades we did.

Todo

• The reverse proxy header configuration is incorrect, or you are accessing Nextcloud from a trusted proxy. If not, this is a security issue and can allow an attacker to spoof their IP address as visible to the Nextcloud. Further information can be found in the documentation (fixed by nextcloud!229 (merged))
• Your web server is not properly set up to resolve "/.well-known/webfinger". Further information can be found in the documentation (!1313 (merged))
• Your web server is not properly set up to resolve "/.well-known/caldav". Further information can be found in the documentation (!1313 (merged))
• Your web server is not properly set up to resolve "/.well-known/carddav". Further information can be found in the documentation (!1313 (merged))

Covered by other issues

• Your installation has no default phone region set. This is required to validate phone numbers in the profile settings without a country code. To allow numbers without a country code, please add "default_phone_region" with the respective ISO 3166-1 code of the region to your config file.

Upstream bugs, waiting to get fixed upstream:

• Module php-imagick in this instance has no SVG support. For better compatibility it is recommended to install it.