Resolve signIn promise when sign in has completed

[johnnyd710]

tldr: Resolve the ElectronRendererAuthorization.signIn() promise when sign-in has fully completed, and reject on errors. Closes #226.

Changes

Previously, some sign-in errors (e.g., an internal server error on the token issuer server) were uncaught by ElectronRendererMain, and there wasn't a way for consumers of this package to catch it. The frontend who initiated the sign-in was left waiting for onAccessTokenChanged forever. Now, we resolve the promise when sign in has actually fully completed or reject the promise if there was an error during sign in, so that the frontend can show an error message.

Technically the API is the same, the types are the same, but the usage could vary slightly.

Example Usage of signIn()

Before

  const onSignInClick = async (): Promise<void> => {
    setSigningIn(true);
    if (IModelApp.authorizationClient instanceof ElectronRendererAuthorization) {
      await IModelApp.authorizationClient.signIn(); // resolves as soon as sign-in starts, with no way to catch errors
    }
  };

  useEffect(() => {
    (IModelApp.authorizationClient as ElectronRendererAuthorization)?.onAccessTokenChanged.addListener(
      (token: AccessToken | undefined) => {
        setAccessToken(token);
        setSigningIn(false);
      }
    );
  });

After

  const onSignInClick = async () => {
    setSigningIn(true);
    if (IModelApp.authorizationClient instanceof ElectronRendererAuthorization) {
      try {
        await IModelApp.authorizationClient.signIn(); // resolves after sign in is complete
      } catch (err) {
        LoggingClient.logException(err); // catch errors and do something
        setErrorMessage("Error while signing in, please try again.");
        setSigningIn(false);
      }
    }
  };

  useEffect(() => {
    (IModelApp.authorizationClient as ElectronRendererAuthorization)?.onAccessTokenChanged.addListener(
      (token: AccessToken | undefined) => {
        setAccessToken(token);
        setSigningIn(false);
      }
    );
  });

[aruniverse]

makes sense

[ben-polinsky]

LGTM, thanks.