Add Ability to Customize redirect parameter names

[justwiebe]

Is your feature request related to a problem? Please describe.

I am using Azure authentication which works great but needs a decent amount of customization. One of these is the redirect.logout parameter name. When I set redirect.logout and log out, the query parameter is "logout_uri=<redirect.logout>" but Azure is expecting "post_logout_redirect_uri=<redirect.logout>".

Describe the solution you'd like to see

It would be nice if the redirect options accepted an object as their value for additional customization. something like:

{
  redirect: {
    callback: '/auth', // still allow strings
    logout: {
      uri: '/', // the actual redirect uri
      param: 'post_logout_redirect_uri' // the query parameter name
    }
  }
}

And the logout URL would now contain &${redirect.logout.param}=${redirect.logout.uri}

Describe alternatives you've considered

As a workaround I'm extending the Scheme and overriding the logout method, but this means that if that method changes I'll have to update it in my code as well because there's no way to simply override the parameter name and call super.

import { Oauth2Scheme } from '@nuxtjs/auth-next/dist/runtime.js'

export default class AzureAdOauth2Scheme extends Oauth2Scheme {
  /**
   * The default logout redirect uri doesn't work for azure, so we have to override this to customize that
   */
  logout() {
    if (this.options.endpoints.logout) {
      const opts = {
        client_id: this.options.clientId + "",
        post_logout_redirect_uri: this.logoutRedirectURI // this is the only line that changed
      };
      const url = this.options.endpoints.logout + "?" + encodeQuery(opts);
      window.location.replace(url);
    }
    return this.$auth.reset();
  }
}