Caches of outside APIs live in /var/cache/sww (closes #314)

The answers of GeoJS, the lists fetched by URL, the DNS blocklists,
AbuseIPDB and routewatch each go in a cache file in SWW_CACHE_DIR
(default /var/cache/sww): lookups.json, lists.json, dnsbl.json,
abuseipdb-scores.json and routewatch.json. reputation.json is gone. The
AbuseIPDB checks spent today are a count, not a cache, and stay in
SWW_STATE_DIR as abuseipdb-checks-spent.json.

A cache file never stops the start: one that does not parse is set
aside as an edit is, one that cannot be read is written over, and its
cache starts empty. An unwritable SWW_CACHE_DIR stops the start, as an
unwritable SWW_STATE_DIR does. Each directory is watched on its own.
The run script makes the cache directory and gives it to sww.

Model: opus-5-5

script/example-app

@@ -9,6 +9,7 @@
 #   - that a probe for /.env bans another client, which its next request bans
 #     for good;
 #   - that only waf's container changes the state directory's owner;
+#   - that waf's container makes the cache directory for the sww user;
 #   - that the app still answers through rproxy with waf stopped, and
 #     that once waf has started again, bans apply again;
 #   - that `sv stop` stops rproxy in order, and `docker stop` stops each
@@ -153,9 +154,9 @@ refused_from() {
     [ "$(status_from "$1" "$2")" = 403 ]
 }
 
-# owner_of_state_dir <container>: print who owns /var/lib/sww there.
-owner_of_state_dir() {
-    docker exec "$1" stat --format '%U' /var/lib/sww
+# owner_of <container> <dir>: print who owns dir there.
+owner_of() {
+    docker exec "$1" stat --format '%U' "$2"
 }
 
 main() {
@@ -173,11 +174,14 @@ main() {
     start_app
     echo "example-app: the health checks pass"
 
-    [ "$(owner_of_state_dir "$WAF")" = sww ] ||
+    [ "$(owner_of "$WAF" /var/lib/sww)" = sww ] ||
         fail "waf's container did not give the state directory to sww"
-    [ "$(owner_of_state_dir "$APP")" = root ] ||
+    [ "$(owner_of "$APP" /var/lib/sww)" = root ] ||
         fail "the app's container changed the state directory's owner"
     echo "example-app: only waf's container changes the state directory's owner"
+    [ "$(owner_of "$WAF" /var/cache/sww)" = sww ] ||
+        fail "waf's container did not make the cache directory for sww"
+    echo "example-app: waf's container makes the cache directory for sww"
 
     page="$(curl --fail --silent --show-error --max-time 10 "http://$address/")" ||
         fail "no answer on port 8080"

script/run

@@ -6,8 +6,9 @@
 # waf listens on port 8090 unless SWW_LISTEN_ADDR says otherwise, and
 # rproxy asks it there unless SWRP_WAF_BACKEND says otherwise. Unless
 # SWW_STATE_DIR is set, the state files go in bin/state, beside the binary,
-# and unless SWW_RULES_DIR is set, the rule files are those of share/rules.d,
-# which the image ships.
+# and unless SWW_CACHE_DIR is set, the cache files go in bin/cache. Unless
+# SWW_RULES_DIR is set, the rule files are those of share/rules.d, which the
+# image ships.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -31,6 +32,11 @@ main() {
         export SWW_STATE_DIR
         mkdir -p "$SWW_STATE_DIR"
     fi
+    if [ -z "${SWW_CACHE_DIR+set}" ]; then
+        SWW_CACHE_DIR="$ROOT/bin/cache"
+        export SWW_CACHE_DIR
+        mkdir -p "$SWW_CACHE_DIR"
+    fi
     if [ -z "${SWW_RULES_DIR+set}" ]; then
         SWW_RULES_DIR="$ROOT/share/rules.d"
         export SWW_RULES_DIR