caddy-frontend: Add Cache Lookup URL to the log

The cluc from https://docs.trafficserver.apache.org/en/7.1.x/admin-guide/logging/formatting.en.html#cache-details
allows to track the log entry per the originated request, which basically
makes debugging of ATS behaviour possible.
5 jobs for feature/caddy-frontend-better-ats-log in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS.SoftwareReleases.IntegrationTest-luke/feature/caddy-frontend-better-ats-log

09:52:34

failed SlapOS.SoftwareReleases.IntegrationTest-luke/feature/caddy-frontend-better-ats-log

11:44:14

failed SlapOS.SoftwareReleases.IntegrationTest-luke/feature/caddy-frontend-better-ats-log

09:53:43

failed SlapOS.SoftwareReleases.IntegrationTest-luke/feature/caddy-frontend-better-ats-log

09:40:22

failed SlapOS.SoftwareReleases.IntegrationTest-luke/feature/caddy-frontend-better-ats-log

09:38:55