V2 alpha - initial version (#172)

Initial alpha codebase for version 2 of WireGuard Portal.
This version is considered unstable and incomplete (for example, no public REST API)! 
Use with care!


Fixes/Implements the following issues:
 - OAuth support #154, #1 
 - New Web UI with internationalisation support #98, #107, #89, #62
 - Postgres Support #49 
 - Improved Email handling #47, #119 
 - DNS Search Domain support #46 
 - Bugfixes #94, #48 

---------

Co-authored-by: Fabian Wechselberger <wechselbergerf@hotmail.com>

internal/app/api/v0/handlers/frontend_config.js.gotpl

@@ -0,0 +1,6 @@
+WGPORTAL_BACKEND_BASE_URL="{{ $.BackendUrl }}";
+WGPORTAL_VERSION="{{ $.Version }}";
+WGPORTAL_SITE_TITLE="{{ $.SiteTitle }}";
+WGPORTAL_SITE_COMPANY_NAME="{{ $.SiteCompanyName }}";
+
+document.title = "{{ $.SiteTitle }}";