Add system activity tracking and event store (#636)

This PR adds system activity tracking. 
The management service records events like 
add/remove peer,  group, rule, route, etc.

The activity events are stored in the SQLite event store
and can be queried by the HTTP API.

management/server/activity/sqlite/sqlite.go

@@ -0,0 +1,149 @@
+package sqlite
+
+import (
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"github.com/netbirdio/netbird/management/server/activity"
+
+	// sqlite driver
+	_ "github.com/mattn/go-sqlite3"
+	"path/filepath"
+	"time"
+)
+
+const (
+	//eventSinkDB is the default name of the events database
+	eventSinkDB      = "events.db"
+	createTableQuery = "CREATE TABLE IF NOT EXISTS events " +
+		"(id INTEGER PRIMARY KEY AUTOINCREMENT, " +
+		"activity INTEGER, " +
+		"timestamp DATETIME, " +
+		"initiator_id TEXT," +
+		"account_id TEXT," +
+		"meta TEXT," +
+		" target_id TEXT);"
+
+	selectStatement = "SELECT id, activity, timestamp, initiator_id, target_id, account_id, meta" +
+		" FROM events WHERE account_id = ? ORDER BY timestamp %s LIMIT ? OFFSET ?;"
+	insertStatement = "INSERT INTO events(activity, timestamp, initiator_id, target_id, account_id, meta) " +
+		"VALUES(?, ?, ?, ?, ?, ?)"
+)
+
+// Store is the implementation of the activity.Store interface backed by SQLite
+type Store struct {
+	db *sql.DB
+}
+
+// NewSQLiteStore creates a new Store with an event table if not exists.
+func NewSQLiteStore(dataDir string) (*Store, error) {
+	dbFile := filepath.Join(dataDir, eventSinkDB)
+	db, err := sql.Open("sqlite3", dbFile)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = db.Exec(createTableQuery)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Store{db: db}, nil
+}
+
+func processResult(result *sql.Rows) ([]*activity.Event, error) {
+	events := make([]*activity.Event, 0)
+	for result.Next() {
+		var id int64
+		var operation activity.Activity
+		var timestamp time.Time
+		var initiator string
+		var target string
+		var account string
+		var jsonMeta string
+		err := result.Scan(&id, &operation, &timestamp, &initiator, &target, &account, &jsonMeta)
+		if err != nil {
+			return nil, err
+		}
+
+		meta := make(map[string]any)
+		if jsonMeta != "" {
+			err = json.Unmarshal([]byte(jsonMeta), &meta)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		events = append(events, &activity.Event{
+			Timestamp:   timestamp,
+			Activity:    operation,
+			ID:          uint64(id),
+			InitiatorID: initiator,
+			TargetID:    target,
+			AccountID:   account,
+			Meta:        meta,
+		})
+	}
+
+	return events, nil
+}
+
+// Get returns "limit" number of events from index ordered descending or ascending by a timestamp
+func (store *Store) Get(accountID string, offset, limit int, descending bool) ([]*activity.Event, error) {
+	order := "DESC"
+	if !descending {
+		order = "ASC"
+	}
+	stmt, err := store.db.Prepare(fmt.Sprintf(selectStatement, order))
+	if err != nil {
+		return nil, err
+	}
+
+	result, err := stmt.Query(accountID, limit, offset)
+	if err != nil {
+		return nil, err
+	}
+
+	defer result.Close() //nolint
+	return processResult(result)
+}
+
+// Save an event in the SQLite events table
+func (store *Store) Save(event *activity.Event) (*activity.Event, error) {
+
+	stmt, err := store.db.Prepare(insertStatement)
+	if err != nil {
+		return nil, err
+	}
+
+	var jsonMeta string
+	if event.Meta != nil {
+		metaBytes, err := json.Marshal(event.Meta)
+		if err != nil {
+			return nil, err
+		}
+		jsonMeta = string(metaBytes)
+	}
+
+	result, err := stmt.Exec(event.Activity, event.Timestamp, event.InitiatorID, event.TargetID, event.AccountID, jsonMeta)
+	if err != nil {
+		return nil, err
+	}
+
+	id, err := result.LastInsertId()
+	if err != nil {
+		return nil, err
+	}
+
+	eventCopy := event.Copy()
+	eventCopy.ID = uint64(id)
+	return eventCopy, nil
+}
+
+// Close the Store
+func (store *Store) Close() error {
+	if store.db != nil {
+		return store.db.Close()
+	}
+	return nil
+}