LDAP: small improvements to various LDAP parts (#17662)

* Add multildap config example

* Publicize mocks for multildap module

pkg/services/multildap/multildap.go

@@ -13,6 +13,9 @@ var GetConfig = ldap.GetConfig
 // IsEnabled checks if LDAP is enabled
 var IsEnabled = ldap.IsEnabled
 
+// newLDAP return instance of the single LDAP server
+var newLDAP = ldap.New
+
 // ErrInvalidCredentials is returned if username and password do not match
 var ErrInvalidCredentials = ldap.ErrInvalidCredentials
 
@@ -22,9 +25,6 @@ var ErrNoLDAPServers = errors.New("No LDAP servers are configured")
 // ErrDidNotFindUser if request for user is unsuccessful
 var ErrDidNotFindUser = errors.New("Did not find a user")
 
-// newLDAP return instance of the single LDAP server
-var newLDAP = ldap.New
-
 // IMultiLDAP is interface for MultiLDAP
 type IMultiLDAP interface {
 	Login(query *models.LoginUserQuery) (