Decouple emailservice from app package (#17827)

* decouple emailservice from app package

* fix some escaped errors

* move email package under app directory

* fix i18n

* reflect review comments

api4/user.go

@@ -1398,8 +1398,8 @@ func updateUserActive(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	if isSelfDeactive {
 		c.App.Srv().Go(func() {
-			if err = c.App.Srv().EmailService.SendDeactivateAccountEmail(user.Email, user.Locale, c.App.GetSiteURL()); err != nil {
-				c.LogErrorByCode(err)
+			if err := c.App.Srv().EmailService.SendDeactivateAccountEmail(user.Email, user.Locale, c.App.GetSiteURL()); err != nil {
+				c.LogErrorByCode(model.NewAppError("SendDeactivateEmail", "api.user.send_deactivate_email_and_forget.failed.error", nil, err.Error(), http.StatusInternalServerError))
 			}
 		})
 	}