mod_unified_push: Add support for multiple token backends, including stoage Now that we have ACLs by default, it is no longer necessary to be completely stateless. On 0.12, using storage has benefits over JWT, because it does not expose client JIDs to the push apps/services. In trunk, PASETO is stateless and does not expose client JIDs.

# Introduction

This module sends a [version query][xep0092] to clients when they
connect, and logs the response, allowing statistics of client usage to
be recorded.

Note that since this is per connection, there will be a bias towards
mobile clients on bad connections.

## Example

    info    Running Running Swift version 4.0