In advance of the PHP 8.3 migration, we'll need to ensure that the presence of the `PHP_ENGINE=8.3` Cookie value (to be set by the WikimediaEvents extension), results in requests being routed to the `-next` releases of mw-web and mw-api-ext.
Following the changes in T391421, the steps are slightly different than when we first introduced `-next` routing for the 8.1 migration (T377042):
[x] Ensure `mw-next-routing` is wired into `profile::trafficserver::backend` as a `trafficserver::lua_script` resource. -- https://gerrit.wikimedia.org/r/1184914
[x] Ensure `mw-next-routing.lua` is wired into the appropriate position (immediately after `multi-dc.lua`) in the plugin chains for the `profile::trafficserver::backend::mapping_rules` entries targeting mw-web and mw-api-ext. -- https://gerrit.wikimedia.org/r/1184915
[x] Ensure `mw-next-routing.lua.conf` targets `"PHP_ENGINE=8.3"` via `cookie_pattern` -- This was done as part of the restructuring in https://gerrit.wikimedia.org/r/1154901.
Once all of these steps are complete and, we're ready to enable external traffic routing to `-next`,. we can set `enabled = true` in `This will involve setting `enabled = true` and `load_fraction = 1.0` in [[ https://gerrit.wikimedia.org/r/plugins/gitiles/operations/puppet/+/refs/heads/production/modules/profile/files/trafficserver/mw-next-routing.lua.conf | mw-next-routing.lua.conf` ]]. Doing so should wait until shortly before we begin the external traffic ramp.