Rename internal/proxy to internal/servewaf (closes #173)

The package passes nothing on since the one-process mode went: it answers rproxy's questions, takes its reports and answers servewaf's own endpoints. It is now named after the command it serves, with `git mv`, and its constructor is `servewaf.New`. `SPEC.md` and the other documents follow. No change of behaviour.

Model: opus-5-5

internal/servewaf/health_test.go

@@ -0,0 +1,40 @@
+package servewaf_test
+
+import (
+	"net/http"
+	"testing"
+
+	"sneak.berlin/go/smallwebwaf/internal/requestlog"
+	"sneak.berlin/go/smallwebwaf/internal/servewaf"
+)
+
+func TestHealthEndpointCountsTowardNoLimit(t *testing.T) {
+	t.Parallel()
+
+	// With a limit of one request a minute, any request counted before
+	// the last one would have it refused.
+	s, _, _ := startWithClock(t, "", map[string]string{rateLimitPerMinute: "1"})
+
+	const (
+		healthChecks = 3
+		contentType  = "text/plain; charset=utf-8"
+	)
+
+	for range healthChecks {
+		got := s.adminRequest("", http.MethodGet, servewaf.HealthPath, "", http.StatusOK)
+
+		if string(got.body) != "ok\n" || got.header.Get("Content-Type") != contentType {
+			t.Errorf("health endpoint answered %q with Content-Type %q, want ok "+
+				"with %q", got.body, got.header.Get("Content-Type"), contentType)
+		}
+	}
+
+	s.get(client, http.StatusOK, requestlog.ActionForward)
+
+	for _, line := range s.out.endedLines(t, healthChecks)[:healthChecks] {
+		if line.ResponseContentType != contentType {
+			t.Errorf("health check's log line has response_content_type %q, "+
+				"want %q", line.ResponseContentType, contentType)
+		}
+	}
+}