feat: JSON access log in the platform logging contract

docker-entrypoint.d/10-config.sh

@@ -23,4 +23,12 @@ for name in $VARS; do
 done
 
 printf 'window.__APP_CONFIG__ = {%s};\n' "$body" > "$OUT"
-echo "10-config.sh: wrote $OUT"
+
+# nginx variables for the JSON access log (nginx/default.conf). Restricted
+# charset: these land inside nginx string literals.
+safe() { printf '%s' "$1" | tr -cd 'A-Za-z0-9._-'; }
+cat > /etc/nginx/conf.d/service-vars.conf <<NGINX
+map \$host \$app_name { default "$(safe "$APP_NAME")"; }
+map \$host \$git_sha { default "$(safe "${GIT_SHA:-dev}")"; }
+NGINX
+echo "10-config.sh: wrote $OUT and service-vars.conf"