Add netflow manager (#3398)

* Add netflow manager

* fix linter issues

client/internal/netflow/store/memory.go

@@ -0,0 +1,48 @@
+package store
+
+import (
+	"sync"
+
+	"github.com/netbirdio/netbird/client/internal/netflow/types"
+)
+
+func NewMemoryStore() *Memory {
+	return &Memory{
+		events: make(map[string]*types.Event),
+	}
+}
+
+type Memory struct {
+	mux    sync.Mutex
+	events map[string]*types.Event
+}
+
+func (m *Memory) StoreEvent(event *types.Event) {
+	m.mux.Lock()
+	defer m.mux.Unlock()
+	m.events[event.ID] = event
+}
+
+func (m *Memory) Close() {
+	m.mux.Lock()
+	defer m.mux.Unlock()
+	m.events = make(map[string]*types.Event)
+}
+
+func (m *Memory) GetEvents() []*types.Event {
+	m.mux.Lock()
+	defer m.mux.Unlock()
+	events := make([]*types.Event, 0, len(m.events))
+	for _, event := range m.events {
+		events = append(events, event)
+	}
+	return events
+}
+
+func (m *Memory) DeleteEvents(ids []string) {
+	m.mux.Lock()
+	defer m.mux.Unlock()
+	for _, id := range ids {
+		delete(m.events, id)
+	}
+}