NewContractInstance accepts a Config and several Nuts engines and returns a new instance of services.ContractClient.

ErrMissingActingParty is returned when the actingPartyCn is missing from the config.

ErrMissingOrganizationKey is used to indicate that this node has no private key of the indicated organization.

ErrMissingPublicURL is returned when the publicUrl is missing from the config.

ErrUnknownSigningMeans is used when the node does not now how to handle the indicated signing means todo move.

Config holds all the configuration params todo this doubles the pkg/Config?.