Extracting email functions into a service (#14802)

* Extracting email functions into a service

* Fixing two shadowing errors

* Address PR review comments

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/ldap.go

@@ -107,7 +107,7 @@ func (a *App) SwitchEmailToLdap(email, password, code, ldapLoginId, ldapPassword
 	}
 
 	a.Srv().Go(func() {
-		if err := a.SendSignInChangeEmail(user.Email, "AD/LDAP", user.Locale, a.GetSiteURL()); err != nil {
+		if err := a.Srv().EmailService.SendSignInChangeEmail(user.Email, "AD/LDAP", user.Locale, a.GetSiteURL()); err != nil {
 			mlog.Error(err.Error())
 		}
 	})
@@ -153,7 +153,7 @@ func (a *App) SwitchLdapToEmail(ldapPassword, code, email, newPassword string) (
 	T := utils.GetUserTranslations(user.Locale)
 
 	a.Srv().Go(func() {
-		if err := a.SendSignInChangeEmail(user.Email, T("api.templates.signin_change_email.body.method_email"), user.Locale, a.GetSiteURL()); err != nil {
+		if err := a.Srv().EmailService.SendSignInChangeEmail(user.Email, T("api.templates.signin_change_email.body.method_email"), user.Locale, a.GetSiteURL()); err != nil {
 			mlog.Error(err.Error())
 		}
 	})