Add Capactior support for native mobile apps

[hmoazzem]

When it comes to OIDC/OAtuh2 in CapacitorJS, the best option probably is https://github.com/capacitor-community/generic-oauth2.

If we're fine using smartphones's default browser (as opposed to UX friendly in-app browser), all we have to do is adjust redirect_uri depending on the platform. Here's snippet from earlier attempt for keycloakjs

this.isIos = Capacitor.isNativePlatform() && Capacitor.getPlatform() === 'ios';
this.isAndroid = Capacitor.isNativePlatform() && Capacitor.getPlatform() === 'android';
this.redirectUri = this.isIos || this.isAndroid ? this.config.redirectUri : (this.config.redirectUriWeb || this.config.redirectUri);