Hello, thanks for contributing! To merge the code you should combine the patches in a single commit and then format the commit message as per contributing guidelines.
To merge the patches you can get the diff of the pull request: * https://patch-diff.githubusercontent.com/raw/kamailio/kamailio/pull/2008.dif...
And apply it to a fresh clone of kamailio master. Then write the commit message based on: * https://github.com/kamailio/kamailio/blob/master/.github/CONTRIBUTING.md#com...
Add also the docs for the new function in the admin guide located in doc/ subfolder of the module.
Given that async sleep is a bit sensitive in usage, add also the async_ms_route() that should be easy as you already said.