Add initial support of device posture checks (#1540)

This PR implements the following posture checks:

* Agent minimum version allowed
* OS minimum version allowed
* Geo-location based on connection IP

For the geo-based location, we rely on GeoLite2 databases which are free IP geolocation databases. MaxMind was tested and we provide a script that easily allows to download of all necessary files, see infrastructure_files/download-geolite2.sh.

The OpenAPI spec should extensively cover the life cycle of current version posture checks.

management/server/geolocation/geolocation_test.go

@@ -0,0 +1,55 @@
+package geolocation
+
+import (
+	"net"
+	"os"
+	"path"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/netbirdio/netbird/util"
+)
+
+// from https://github.com/maxmind/MaxMind-DB/blob/main/test-data/GeoLite2-City-Test.mmdb
+var mmdbPath = "../testdata/GeoLite2-City-Test.mmdb"
+
+func TestGeoLite_Lookup(t *testing.T) {
+	tempDir := t.TempDir()
+	filename := path.Join(tempDir, MMDBFileName)
+	err := util.CopyFileContents(mmdbPath, filename)
+	assert.NoError(t, err)
+	defer func() {
+		err := os.Remove(filename)
+		if err != nil {
+			t.Errorf("os.Remove: %s", err)
+		}
+	}()
+
+	db, err := openDB(mmdbPath)
+	assert.NoError(t, err)
+
+	geo := &Geolocation{
+		mux:    sync.RWMutex{},
+		db:     db,
+		stopCh: make(chan struct{}),
+	}
+	assert.NotNil(t, geo)
+	defer func() {
+		err = geo.Stop()
+		if err != nil {
+			t.Errorf("geo.Stop: %s", err)
+		}
+	}()
+
+	record, err := geo.Lookup(net.ParseIP("89.160.20.128"))
+	assert.NoError(t, err)
+	assert.NotNil(t, record)
+	assert.Equal(t, "SE", record.Country.ISOCode)
+	assert.Equal(t, uint(2661886), record.Country.GeonameID)
+	assert.Equal(t, "Linköping", record.City.Names.En)
+	assert.Equal(t, uint(2694762), record.City.GeonameID)
+	assert.Equal(t, "EU", record.Continent.Code)
+	assert.Equal(t, uint(6255148), record.Continent.GeonameID)
+}