Feature request: Clones with custom ports

Goal

Creating a new clone is always taking the next free port in a given range in the configuration. The possibility to create a clone with a custom port would give users the chance to keep their (local) connection configurations and make the usage more comfortable. The idea is to add a validated input field for a custom port. The input is validated against the port range in the configuration and whether the port is free. Via API the clone is either created or the response is an error. If no custom port is given the standard behaviour is used.