Additional OAuth2 providers (#1010)

* add google+

* sort signin oauth2 providers based on the name so order is always the same

* update auth tip for google+

* add gitlab provider

* add bitbucket provider (and some go fmt)

* add twitter provider

* add facebook provider

* add dropbox provider

* add openid connect provider incl. new format of tips section in "Add New Source"

* lower the amount of disk storage for each session to prevent issues while building cross platform (and disk overflow)

* imports according to goimport and code style

* make it possible to set custom urls to gitlab and github provider (only these could have a different host)

* split up oauth2 into multiple files

* small typo in comment

* fix indention

* fix indentation

* fix new line before external import

* fix layout of signin part

* update "broken" dependency

modules/auth/auth_form.go

@@ -11,34 +11,40 @@ import (
 
 // AuthenticationForm form for authentication
 type AuthenticationForm struct {
-	ID                int64
-	Type              int    `binding:"Range(2,6)"`
-	Name              string `binding:"Required;MaxSize(30)"`
-	Host              string
-	Port              int
-	BindDN            string
-	BindPassword      string
-	UserBase          string
-	UserDN            string
-	AttributeUsername string
-	AttributeName     string
-	AttributeSurname  string
-	AttributeMail     string
-	AttributesInBind  bool
-	Filter            string
-	AdminFilter       string
-	IsActive          bool
-	SMTPAuth          string
-	SMTPHost          string
-	SMTPPort          int
-	AllowedDomains    string
-	SecurityProtocol  int `binding:"Range(0,2)"`
-	TLS               bool
-	SkipVerify        bool
-	PAMServiceName    string
-	Oauth2Provider    string
-	Oauth2Key         string
-	Oauth2Secret      string
+	ID                            int64
+	Type                          int    `binding:"Range(2,6)"`
+	Name                          string `binding:"Required;MaxSize(30)"`
+	Host                          string
+	Port                          int
+	BindDN                        string
+	BindPassword                  string
+	UserBase                      string
+	UserDN                        string
+	AttributeUsername             string
+	AttributeName                 string
+	AttributeSurname              string
+	AttributeMail                 string
+	AttributesInBind              bool
+	Filter                        string
+	AdminFilter                   string
+	IsActive                      bool
+	SMTPAuth                      string
+	SMTPHost                      string
+	SMTPPort                      int
+	AllowedDomains                string
+	SecurityProtocol              int `binding:"Range(0,2)"`
+	TLS                           bool
+	SkipVerify                    bool
+	PAMServiceName                string
+	Oauth2Provider                string
+	Oauth2Key                     string
+	Oauth2Secret                  string
+	OpenIDConnectAutoDiscoveryURL string
+	Oauth2UseCustomURL            bool
+	Oauth2TokenURL                string
+	Oauth2AuthURL                 string
+	Oauth2ProfileURL              string
+	Oauth2EmailURL                string
 }
 
 // Validate validates fields