MM-4998 Adding LoginIdAttribute to allow LDAP users to change their login ID without losing their account (#8756)

* Adding LoginIdAttribute

* Modifying LDAP to use loginIDAttribute.

* Adding IDAttribute migration and AD objectGUID support.

* Removing unused idea.

* Fix typo.

einterfaces/ldap.go

@@ -4,8 +4,6 @@
 package einterfaces
 
 import (
-	"github.com/go-ldap/ldap"
-
 	"github.com/mattermost/mattermost-server/model"
 )
 
@@ -14,12 +12,11 @@ type LdapInterface interface {
 	GetUser(id string) (*model.User, *model.AppError)
 	GetUserAttributes(id string, attributes []string) (map[string]string, *model.AppError)
 	CheckPassword(id string, password string) *model.AppError
+	CheckPasswordAuthData(authData string, password string) *model.AppError
 	SwitchToLdap(userId, ldapId, ldapPassword string) *model.AppError
 	ValidateFilter(filter string) *model.AppError
 	StartSynchronizeJob(waitForJobToFinish bool) (*model.Job, *model.AppError)
 	RunTest() *model.AppError
 	GetAllLdapUsers() ([]*model.User, *model.AppError)
-	UserFromLdapUser(ldapUser *ldap.Entry) *model.User
-	UserHasUpdateFromLdap(existingUser *model.User, currentLdapUser *model.User) bool
-	UpdateLocalLdapUser(existingUser *model.User, currentLdapUser *model.User) *model.User
+	MigrateIDAttribute(toAttribute string) error
 }