feat(workflow): support limit count action

apisix/plugins/workflow.lua

@@ -117,6 +117,10 @@ function _M.check_schema(conf)
                 return false, "failed to validate the '" .. action[1] .. "' action: " .. err
             end
 
+            if action[1] == "limit-count" and action[2]["group"] then
+                return false, "failed to validate the '" .. action[1] .. "' action: group is not supported in workflow"
+            end
+
             -- use the action's idx as an identifier to isolate between confs
             action[2]["_vid"] = idx
        end