doc: Describe how to configure loglevels via configuration

[fgheysels]

We should have some documentation which informs people how we can configure the loglevels at runtime / via the configuration.

[stijnmoreels]

Isn't that Serilog's resposibility? Don't think that we every have extensions for configuring such log levels? We chould, however, link to Serilog's pages, though.
https://github.com/serilog/serilog/wiki/Configuration-Basics#minimum-level and the LoggingLevelSwitch.

[fgheysels]

Yes, that is true.
However, I think we can already make an improvement by making sure that the setup of serilog in the templates that we provide, is done by reading logging settings from the configuration.
Cfr arcus-azure/arcus.templates#480

[stijnmoreels]

Yes, was also experimenting with that, but we have to wait until Serilog is fully .NET 6 supported, as mentioned in this issue: arcus-azure/arcus.templates#480 (comment)