[feature] Add a request ID and include it in logs (#1476)

This adds a lightweight form of tracing to GTS. Each incoming request is
assigned a Request ID which we then pass on and log in all our log
lines. Any function that gets called downstream from an HTTP handler
should now emit a requestID=value pair whenever it logs something.

Co-authored-by: kim <grufwub@gmail.com>

web/template/error.tmpl

@@ -20,6 +20,7 @@
     <main>
         <section class="error">
           <span>❌</span> <pre>{{.error}}</pre>
+          <span>Request ID</span> <code>{{.requestID}}</code>
         </section>
     </main>
 {{ template "footer.tmpl" .}}