rproxy and servewaf replace the one-process smallwebwaf (closes #172, closes #165)

`smallwebwaf` with no command now prints the commands and exits with status 2.
The image runs rproxy, or servewaf with SMALLWEBWAF_COMMAND=servewaf. The
passing-on code, its settings and its log fields and metric go. internal/proxy
keeps the checks, answers, reports and own endpoints; its tests run through the
real rproxy. The documents describe the pair.

Judgement call: clients.json keeps token_refused, since state files refuse unknown fields.
Deviation: script/gitea-requests sets SWWAF_LOG_REQUEST_HEADERS, to label requests.
Partially verified: make example-app and make gitea-requests never built the image, as Ubuntu's snapshot service answered 5xx.

Model: opus-5-5

internal/proxy/countries_test.go

@@ -65,7 +65,7 @@ func TestCountryLists(t *testing.T) {
 				req.Header.Set(forwardedFor, sent.client)
 				got := do(t, req)
 
-				line := out.requestLines(t, i+1)[i]
+				line := out.endedLines(t, i+1)[i]
 				if line.ASN != sent.asn || line.ASName != sent.asName ||
 					line.Country != sent.country {
 					t.Errorf("log line has %q, %q and %q, want %q, %q and %q",
@@ -90,7 +90,7 @@ func TestCountryLists(t *testing.T) {
 	}
 }
 
-func TestCountryRefusalComesBeforeTheBody(t *testing.T) {
+func TestCountryRefusalKeepsARequestFromTheApp(t *testing.T) {
 	t.Parallel()
 
 	var calls atomic.Int32
@@ -109,13 +109,9 @@ func TestCountryRefusalComesBeforeTheBody(t *testing.T) {
 	req.Header.Set(forwardedFor, fromKP)
 	wantStatus(t, do(t, req), http.StatusForbidden)
 
-	line := out.requestLine(t)
+	line := out.endedLine(t)
 	wantLine(t, line, http.StatusForbidden, requestlog.ActionCountryDenied)
 
-	if line.RequestBytes != 0 {
-		t.Errorf("log line has request_bytes %d, want 0", line.RequestBytes)
-	}
-
 	if calls.Load() != 0 {
 		t.Errorf("the app was called %d times, want none", calls.Load())
 	}
@@ -211,7 +207,7 @@ func TestPrivateAddressIsNeverLookedUp(t *testing.T) {
 
 				wantStatus(t, do(t, req), http.StatusOK)
 
-				line := out.requestLines(t, i+1)[i]
+				line := out.endedLines(t, i+1)[i]
 				wantLine(t, line, http.StatusOK, requestlog.ActionForward)
 
 				for _, field := range []string{"asn", "as_name", "country"} {