MM-39591 - Restore custom message for guest invites (#18849)

app/email/email.go

@@ -515,6 +515,11 @@ func (es *Service) SendGuestInviteEmails(team *model.Team, channels []*model.Cha
 			data.Props["Title"] = i18n.T("api.templates.invite_body.title", map[string]interface{}{"SenderName": senderName, "TeamDisplayName": team.DisplayName})
 			data.Props["SubTitle"] = i18n.T("api.templates.invite_body_guest.subTitle")
 			data.Props["Button"] = i18n.T("api.templates.invite_body.button")
+			data.Props["SenderName"] = senderName
+			data.Props["Message"] = ""
+			if message != "" {
+				data.Props["Message"] = message
+			}
 			data.Props["InviteFooterTitle"] = i18n.T("api.templates.invite_body_footer.title")
 			data.Props["InviteFooterInfo"] = i18n.T("api.templates.invite_body_footer.info")
 			data.Props["InviteFooterLearnMore"] = i18n.T("api.templates.invite_body_footer.learn_more")