* Added external auth provider that calls a configurable program
Closes#19975
* Raise proper InvalidAuth exception on OSError during program execution
* Changed name of external auth provider to command_line
* Renamed program config option to command in command_line auth provider
* Made meta variable parsing in command_line auth provider optional
* Added tests for command_line auth provider
* Fixed indentation
* Suppressed wrong pylint warning
* Fixed linting
* Added test for command line auth provider login flow
* Log error when user fails authentication
* Use %r formatter instead of explicit repr()
* Mix all used names of typing module into module namespace
I consider this nasty and bad coding style, but was requested by
@awarecan for consistency with the remaining codebase.
* Small code style change
* Strip usernames with command_line auth provider
Robert Schindler