Implement MVP for sending of transcations to Sovereign rollups

[soareschen]

Part of: #10
Prerequisites: #96

Summary

One of the first things the relayer must support is to be able to send transactions to a Sovereign rollup. However, a complication for this task is that it is still unclear how the relayer can communicate with a third-party rollup sequencer, and whether the third-party sequencer API would be the same as the APIs defined in Sovereign SDK.

In this task, we will work around the uncertainty by assuming that the relayer would be running the rollup node also as a dedicated sequencer node. This means that the relayer operator must register themselves as a sequencer, and submit IBC transactions as dedicated blobs to Celestia directly. The Hermes relayer can only support third-party sequencers, if we have clear specifications on how such sequencers would operate.

The task would involve the following:

• Encode transactions as JSON RPC payloads
• Submit transactions using the sequencer_publishBatch and/or the sequencer_acceptTx JSON RPC methods.
• Find ways to poll/query for the transaction status
• If possible, get the transaction events.
  • If there is no simple way to retrieve the transaction events, the implement should first return empty list of events for the purpose of this issue. We can create follow up issues to retrieve transaction events.
• It is not clear how to simulate TX and estimate fees for Sovereign rollup. If there is no clear approach, the PR of this issue should use a hardcoded fee as a MVP.

The tests for sending transactions can be done as specified in #99, either in the same PR or in a follow up PR.