store unknown servers in the invitation process answer and finalize + server storage fixes and testing

client/serverstorage.go

@@ -55,6 +55,39 @@ func (ss *ServerStorage) StoreServer(sc *Server) error {
 
 }
 
+// Check if a server exists in a badger database with Server.GetUid() as key
+func (ss *ServerStorage) ServerExists(sc *Server) (bool, error) {
+	err := ss.open()
+	if err != nil {
+		return false, err
+	}
+	defer ss.close()
+
+	shakey := sha256.Sum256([]byte(sc.GetServerCard().GetUid()))
+	key := shakey[:]
+	// check if key exists in badger database
+	err = ss.db.View(func(txn *badger.Txn) error {
+		_, err := txn.Get(key)
+		return err
+	}) // Add a comma here
+	if err != nil { // key does not exist
+		return false, nil
+	}
+	return true, nil
+}
+
+// Store a server in a badger database with Server.GetUid() as key if it is not already there
+func (ss *ServerStorage) StoreServerIfNotExists(sc *Server) error {
+	exists, err := ss.ServerExists(sc)
+	if err != nil {
+		return err
+	}
+	if !exists {
+		return ss.StoreServer(sc)
+	}
+	return nil
+}
+
 // LoadServer function loads a Server from a badger database with Server.GetUid() as key
 func (ss *ServerStorage) LoadServer(uid string) (*Server, error) {
 	var sc Server