async connect() {
    const { Client } = this;
    if (!Client) {
      throw new Error('Does not support persistent connection');
    }
    this.client = new Client(this.connection);
    await this.client.connect();
    this.connectedAt = new Date();
    this.lastActivityAt = new Date();
    this.keepAlive();
  }
Create a persistent database connection if the driver implementation supports it.