Additional metadata for the transport configuration.
This can include any key-value pairs relevant to the chosen transport mode.
Transport mode. One of ESPTransportMode for built-in transports,
or an arbitrary string key for a custom transport registered via
customTransportManagers on the node.
Configuration options for the transport mechanism for ESP communication.
Includes the transport type and any additional metadata for the chosen mode (e.g.
baseUrl,securityType,pop,protocolfor the local transport).