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/domain/auth.go

@@ -0,0 +1,51 @@
+package domain
+
+import (
+	"context"
+
+	"golang.org/x/oauth2"
+)
+
+type LoginProvider string
+
+type LoginProviderInfo struct {
+	Identifier  string
+	Name        string
+	ProviderUrl string
+	CallbackUrl string
+}
+
+type AuthenticatorUserInfo struct {
+	Identifier UserIdentifier
+	Email      string
+	Firstname  string
+	Lastname   string
+	Phone      string
+	Department string
+	IsAdmin    bool
+}
+
+type AuthenticatorType string
+
+const (
+	AuthenticatorTypeOAuth AuthenticatorType = "oauth"
+	AuthenticatorTypeOidc  AuthenticatorType = "oidc"
+)
+
+type OauthAuthenticator interface {
+	GetName() string
+	GetType() AuthenticatorType
+	AuthCodeURL(state string, opts ...oauth2.AuthCodeOption) string
+	Exchange(ctx context.Context, code string, opts ...oauth2.AuthCodeOption) (*oauth2.Token, error)
+	GetUserInfo(ctx context.Context, token *oauth2.Token, nonce string) (map[string]interface{}, error)
+	ParseUserInfo(raw map[string]interface{}) (*AuthenticatorUserInfo, error)
+	RegistrationEnabled() bool
+}
+
+type LdapAuthenticator interface {
+	GetName() string
+	PlaintextAuthentication(userId UserIdentifier, plainPassword string) error
+	GetUserInfo(ctx context.Context, username UserIdentifier) (map[string]interface{}, error)
+	ParseUserInfo(raw map[string]interface{}) (*AuthenticatorUserInfo, error)
+	RegistrationEnabled() bool
+}