Mask a target URL's query string when the URL has no path (closes #500)

`urlSecrets` treated a target URL's request URI as a secret only when the URL had a path, so for a target URL such as `https://example.com/?token=…` a response echoing the request line showed the token in the event log and on the event's page. It now also treats the query string, and the request URI that carries it, as secrets whenever the URL has one, whatever its path. With "Pass the query string on to this target" on, only the target's own part is masked, not the event's. A URL with a path is masked as before. As for paths and userinfo, no length floor applies.

Model: opus-5-5

internal/delivery/target_redact_test.go

@@ -202,6 +202,48 @@ func TestRedactor_RemovesHTTPURLQueryAndUserinfo(t *testing.T) {
 	}
 }
 
+// TestRedactor_RemovesEchoedQueryOfURLWithoutPath covers an
+// HTTP target URL whose credential is all in its query string.
+// Written with or without the "/", the request line sends it
+// as "/?token=…", and a target passing the event's query string
+// on sends that after an "&". The event's part stays visible:
+// the event's page shows it anyway.
+func TestRedactor_RemovesEchoedQueryOfURLWithoutPath(t *testing.T) {
+	t.Parallel()
+
+	const secret = "s3cr3t"
+
+	marker := delivery.RedactionMarker
+
+	// An echoed request line, and what the event log shows of it.
+	echoes := map[string]string{
+		"POST /?token=" + secret + " HTTP/1.1": "POST " + marker +
+			" HTTP/1.1",
+		"POST ?token=" + secret + " HTTP/1.1": "POST ?" + marker +
+			" HTTP/1.1",
+		"POST /?token=" + secret + "&a=1&b=2 HTTP/1.1": "POST " +
+			marker + "&a=1&b=2 HTTP/1.1",
+		"POST ?token=" + secret + "&a=1&b=2 HTTP/1.1": "POST ?" +
+			marker + "&a=1&b=2 HTTP/1.1",
+	}
+
+	for _, dest := range []string{
+		"https://example.com/?token=" + secret,
+		"https://example.com?token=" + secret,
+	} {
+		r := delivery.NewRedactor(&database.Target{
+			Type:   database.TargetTypeHTTP,
+			Config: `{"url":"` + dest + `"}`,
+		})
+
+		for echoed, want := range echoes {
+			assert.Equal(
+				t, want, r.Redact(echoed), "%s: %s", dest, echoed,
+			)
+		}
+	}
+}
+
 // TestRedactor_LeavesUnrelatedTextAlone pins that the
 // redactor matches literally: it does not guess at what a
 // secret looks like, so ordinary response content survives.