Documentation addition for edge case

[mattrjensen]

Great plugin, thanks.

Suggest you add to your documentation about the plugin, that if users are experiencing 404 errors on the wp-login.php page (404.15 errors, to be precise), that it may be because AAD is returning a URL greater than the IIS default maximum of 2000. We were experiencing this error as a result of using the plugin, and increasing the URL maximum resolved this issue.

This can be done in web.config, eg.:

<configuration>

        <system.webServer>
            <security>
                <requestFiltering>
                    <!-- Fix 404 error when querystring is too long when AAD redirects with code & token -->
                    <requestLimits maxQueryString="3000"/>
                </requestFiltering>
            </security>
        </system.webServer>
    </configuration>`