Add paging headers (#36521)

Adds support for paging in admin/hooks api endpoint

fixes: https://github.com/go-gitea/gitea/issues/36516

---------

Co-authored-by: techknowlogick <techknowlogick@gitea.com>
Co-authored-by: techknowlogick <matti@mdranta.net>

routers/api/v1/user/action.go

@@ -333,10 +333,10 @@ func ListVariables(ctx *context.APIContext) {
 	//     "$ref": "#/responses/error"
 	//   "404":
 	//     "$ref": "#/responses/notFound"
-
+	listOptions := utils.GetListOptions(ctx)
 	vars, count, err := db.FindAndCount[actions_model.ActionVariable](ctx, &actions_model.FindVariablesOpts{
 		OwnerID:     ctx.Doer.ID,
-		ListOptions: utils.GetListOptions(ctx),
+		ListOptions: listOptions,
 	})
 	if err != nil {
 		ctx.APIErrorInternal(err)
@@ -354,6 +354,7 @@ func ListVariables(ctx *context.APIContext) {
 		}
 	}
 
+	ctx.SetLinkHeader(int(count), listOptions.PageSize)
 	ctx.SetTotalCountHeader(count)
 	ctx.JSON(http.StatusOK, variables)
 }