Return information about the tx submitted (if submitted, hash)

[rmeissner]

After a Safe app submitted a transaction it should get the safeTxHash of that transaction in return. This way it can request information about this transaction at a later point in time.

Why would we want this?

Currently the Safe app is closed after a transaction has been submitted (switch to transactions tab). Also there is no way for the Safe app to check if the transaction has been accepted or not.

Notes?

For this it is required to add some way to connect events to the protocol (similar to the ID field in the json rpc request). This is required for many of the features in this document and could even be its own feature.