add api data() for inbound_lane

[xiaoch05]

in outbound lane we have opened the data() api
but in the inbound lane this api is not opened, it's very useful for application using the bridge.

[cla-bot-2021]

User @xiaoch05, please sign the CLA here.

[svyatonik]

it's very useful for application using the bridge.

@xiaoch05 Is there an example of such application? InboundLane is a private struct, so you application must be somewhere in the pallet code, right? Can you provide us with details of you app and how it uses the InboundLane? The fact is that this commit generates annoying compilation warning and unless we'll have a strong evidence of how/why it is used, I'd like this commit to be reverted.

Thank you!

[xiaoch05]

it's very useful for application using the bridge.

@xiaoch05 Is there an example of such application? InboundLane is a private struct, so you application must be somewhere in the pallet code, right? Can you provide us with details of you app and how it uses the InboundLane? The fact is that this commit generates annoying compilation warning and unless we'll have a strong evidence of how/why it is used, I'd like this commit to be reverted.

Thank you!

Hi @svyatonik , the previous version supported getting this interface for InboundLane, and we were using it here, emitting an event to correspond with the message in the source chain. But I find that we are able to get all the information we need from these events https://github.com/paritytech/parity-bridges-common/blob/master/modules/dispatch/src/lib.rs#L114-L135, so I changed my previous thought that this interface is not that important for the application. If there is a compilation warning, I think it would be better to revert this modification too.

[svyatonik]

Thank you. Yep, I'll revert it then to avoid unnecessary warnings :)