The collation generation subsystem is the interface between polkadot and the collators.

Protocol

On every ActiveLeavesUpdate:

• If there is no collation generation config, ignore.
• Otherwise, for each activated head in the update:
• Determine if the para is scheduled on any core by fetching the availability_cores Runtime API.
• Use the Runtime API subsystem to fetch the full validation data.
• Invoke the collator, and use its outputs to produce a [CandidateReceipt], signed with the configuration's key.
• Dispatch a [CollatorProtocolMessage::DistributeCollation](receipt, pov).