Webhook Logs show proper HTTP Method, and allow change HTTP method in form (#6953)

* Fix #6951 - logs show proper HTTP Method, and allow change HTTP method
in form

* enforce POST method for webhook

* set default if method is empty

routers/api/v1/utils/hook.go

@@ -98,6 +98,7 @@ func addHook(ctx *context.APIContext, form *api.CreateHookOption, orgID, repoID
 		URL:         form.Config["url"],
 		ContentType: models.ToHookContentType(form.Config["content_type"]),
 		Secret:      form.Config["secret"],
+		HTTPMethod:  "POST",
 		HookEvent: &models.HookEvent{
 			ChooseEvents: true,
 			HookEvents: models.HookEvents{