Say the proxy is covered by default or by a set value

The rate-limit test comments on trustedProxyCIDR and forwardedKeyFor
said production needs TRUSTED_PROXIES set; another said only
operator-listed addresses are trusted. The README's Rate Limiting
paragraph said "listed in", and the login endpoint section assumed
every proxied deployment shares one bucket. All now match the
RFC 1918 default.

Model: opus-5-5

internal/middleware/ratelimit_test.go

@@ -384,8 +384,8 @@ const (
 	// trustedProxyCIDR is the proxy network the forwarded-path
 	// tests configure, and trustedPeer an address inside it. A
 	// production deployment is required to run behind a reverse
-	// proxy with TRUSTED_PROXIES set, so this is the shape the
-	// bucketing has to hold in.
+	// proxy that TRUSTED_PROXIES covers, either by the default or by
+	// a set value, so this is the shape the bucketing has to hold in.
 	trustedProxyCIDR = "10.0.0.0/8"
 	trustedPeer      = "10.0.0.1:44444"
 )
@@ -1097,8 +1097,9 @@ func TestPostRateLimit_IPv4IndependentPerAddress(t *testing.T) {
 // that arrives from trustedPeer — a configured trusted proxy — and
 // names forwarded as its client in X-Forwarded-For. That is the
 // production path: a deployment is required to run behind a reverse
-// proxy with TRUSTED_PROXIES set, so the forwarded address, not the
-// peer, is what the limiters bucket on there.
+// proxy that TRUSTED_PROXIES covers, either by the default or by a
+// set value, so the forwarded address, not the peer, is what the
+// limiters bucket on there.
 func forwardedKeyFor(
 	t *testing.T, m *middleware.Middleware, forwarded string,
 ) string {
@@ -1178,9 +1179,9 @@ func TestRateLimitKey_ForwardedIPv6BucketsByPrefix(t *testing.T) {
 //
 // Every existing test of this fallback uses an IPv4 proxy, where
 // bucketKey is the identity function, so replacing the call with
-// peer.String() leaves the whole suite green. Only operator-listed
-// addresses reach this line and the fallback is fail-closed, so this
-// pins behaviour rather than fixing a defect.
+// peer.String() leaves the whole suite green. Only addresses inside
+// TRUSTED_PROXIES reach this line and the fallback is fail-closed, so
+// this pins behaviour rather than fixing a defect.
 func TestRateLimitKey_TrustedPeerUnusableForwardedMasksPeer(
 	t *testing.T,
 ) {