Provide an alternative way to start OAuth flow #89
Description
The OAuth flow opens a browser with the authorize URL, but opening a browser may fail.
Any errors that may occur when opening a browser must be handled, and the "waiting" page in the app should provide (1) a way to re-open the browser with the same URL and (2) a way to copy the URL to the clipboard. These options must be provided even when no error occurred opening the browser.
Specifically, an error that may occur is that Process.Start() may throw an Win32Exception. This should not make the application crash.