Look clients up in the IPinfo Lite file with SWWAF_LOOKUP_SOURCE=file (closes #22)

SWWAF_LOOKUP_SOURCE=file looks every client up in the file
SWWAF_LOOKUP_DB_PATH names, without GeoJS. file without the path, the
path with another source, or a file that cannot be read stops the start.
The file is read whole into memory, so overwriting it in place cannot
disturb a lookup, and read again 2 seconds after its last change; a
replacement that cannot be read is logged, counted and sent as a
file_error alert, and the old one stays in use. Metrics give when it
was read and the failed reads. Tests write their databases through
internal/lookup/lookuptest.

Deviation: go.mod and go.sum written by hand; go runs only through make.
Judgement call: the 2-second wait, as the rule files have.

Model: opus-5-5

internal/proxy/proxy_test.go

@@ -16,6 +16,7 @@ import (
 
 	"sneak.berlin/go/smallwebwaf/internal/alerts"
 	"sneak.berlin/go/smallwebwaf/internal/config"
+	"sneak.berlin/go/smallwebwaf/internal/lookup"
 	"sneak.berlin/go/smallwebwaf/internal/proxy"
 	"sneak.berlin/go/smallwebwaf/internal/requestlog"
 	"sneak.berlin/go/smallwebwaf/internal/rules"
@@ -67,6 +68,7 @@ const (
 	rateLimitPerDay         = "SWWAF_RATE_LIMIT_PER_DAY"
 	rateLimitExemptPaths    = "SWWAF_RATE_LIMIT_EXEMPT_PATHS"
 	lookupSource            = "SWWAF_LOOKUP_SOURCE"
+	lookupDBPath            = "SWWAF_LOOKUP_DB_PATH"
 	lookupTimeout           = "SWWAF_LOOKUP_TIMEOUT"
 	addLookupHeaders        = "SWWAF_ADD_LOOKUP_HEADERS"
 	deniedCountries         = "SWWAF_DENIED_COUNTRIES"
@@ -265,7 +267,8 @@ func startProxyWithAlerts(
 // proxy raises, as the settings in env make it. No alert is sent from the
 // queue: they wait in it, for the test to look at. With no geojsURL, there
 // is no stand-in for GeoJS to look clients up at, and SWWAF_LOOKUP_SOURCE
-// is off unless env sets it.
+// is off unless env sets it. While it is file, the lookup database
+// SWWAF_LOOKUP_DB_PATH names is read.
 func newProxy(
 	t *testing.T, appURL, geojsURL string, now func() time.Time,
 	env map[string]string,
@@ -310,11 +313,23 @@ func newProxy(
 		ProcessLog: processLog,
 	})
 
+	var lookupFile *lookup.File
+
+	if cfg.LookupSource == "file" {
+		lookupFile, err = lookup.OpenFile(lookup.FileParams{
+			Path: cfg.LookupDBPath, Now: now, ProcessLog: processLog, Alerts: alertQueue,
+		})
+		if err != nil {
+			t.Fatalf("lookup database: %v", err)
+		}
+	}
+
 	server := proxy.New(proxy.Params{
 		Config:     cfg,
 		RequestLog: out,
 		ProcessLog: processLog,
 		GeoJSURL:   geojsURL,
+		LookupFile: lookupFile,
 		Now:        now,
 		Rules:      ruleFiles,
 		Alerts:     alertQueue,