Add GeoIP support for unique IP aggregation

- Introduced GeoIP configuration options in config.example.yaml to enable geolocation lookups for the /api/agg/unique-ips endpoint.
- Updated the aggregate handler to include optional GeoIP data in responses, enriching unique IP information with country and city details, as well as ASN data if available.
- Enhanced documentation in AGGREGATE.md and README.md to reflect the new GeoIP functionality and its usage.
- Added a dependency on the geoip2-golang library in go.mod for GeoIP lookups.
- Modified tests to accommodate the new GeoIP integration in the aggregate handler.

internal/server/gateway.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/telemt/telemt-api/internal/aggregate"
 	"github.com/telemt/telemt-api/internal/config"
+	"github.com/telemt/telemt-api/internal/geoip"
 	"github.com/telemt/telemt-api/internal/proxy"
 )
 
@@ -23,13 +24,14 @@ type Gateway struct {
 	parsed        *config.Parsed
 	proxies       map[string]*httputil.ReverseProxy
 	agg           *aggregate.Handler
+	geo           *geoip.Service
 	log           *slog.Logger
 	transport     *http.Transport
 	promHandler   http.Handler
 }
 
 // NewGateway builds handlers and reverse proxies from parsed config.
-func NewGateway(p *config.Parsed, log *slog.Logger) (*Gateway, error) {
+func NewGateway(p *config.Parsed, log *slog.Logger, geo *geoip.Service) (*Gateway, error) {
 	t := proxy.DirectTransport()
 	t.MaxIdleConns = 64
 	t.IdleConnTimeout = 90 * time.Second
@@ -40,6 +42,7 @@ func NewGateway(p *config.Parsed, log *slog.Logger) (*Gateway, error) {
 	g := &Gateway{
 		parsed:      p,
 		proxies:     make(map[string]*httputil.ReverseProxy),
+		geo:         geo,
 		log:         log,
 		transport:   t,
 		promHandler: promhttp.Handler(),
@@ -65,7 +68,7 @@ func NewGateway(p *config.Parsed, log *slog.Logger) (*Gateway, error) {
 		}
 		g.proxies[s.Alias] = rp
 	}
-	g.agg = aggregate.NewHandler(p, &http.Client{Transport: t})
+	g.agg = aggregate.NewHandler(p, &http.Client{Transport: t}, geo)
 	return g, nil
 }
 
@@ -222,5 +225,8 @@ func (s *statusWriter) WriteHeader(code int) {
 // Shutdown idle connections on the shared transport.
 func (g *Gateway) Shutdown(ctx context.Context) error {
 	g.transport.CloseIdleConnections()
+	if g.geo != nil {
+		_ = g.geo.Close()
+	}
 	return nil
 }