Read settings from $PSScriptRoot/config/config.json?

[haxtibal]

We currently set https port and timeout either from command line arguments, or set them to default if not given.

The original Invoke-IcingaApiChecksRESTCall instead reads a config.json file from e.g. C:/Program Files/WindowsPowerShell/Modules/icinga-powershell-framework/config/config.json to determine those values.

This involves figuring out where $PSScriptRoot is, and introduces a dependency on another JSON interface, which I'd rather avoid. But if someone thinks evaluating config.json is important, leave a note here and I may consider adding it anyway.