I have the same issue. I need a fixed redirect_uri for my client configuration at an authority server. I have managed to get this fixed redirect_uri by identity.getRedirectURL() (derived from the add-on’s ID) (as described here https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/identity)
e.g.
https://.extensions.allizom.org/
This URL is not reachable and it seems that only identity.launchWebAuthFlow knows how to interpret it.
However, I cannot use launchWebAuthFlow because I don’t want WebAuthFlow… I want SignInRedirect (~using other js libraries e.g. oidc-client, okta, …). The OAuth flow doesn’t continue its dance with this https://…extensions.allizom.org as a redirect_uri.
I could work around it by using webRequest.onBeforeRequest to observe any GET to this url. But I find it a little hacky and don’t feel like this is the right way to use identity.getRedirectURL() as intended by the Firefox team.
What is the intended use of identity.getRedirectURL()?
Thanks in advance!