We can now pass more than one set of `nonce_pks` when creating a CFD.
Each set corresponds to (and is identified by) a different oracle
event, allowing us to construct CFDs which can be settled via oracle
attestation at more than one point in time.
We also remember the CET-event relationship in `CfdTransactions`. This
is needed so that we can select the correct CET when the oracle
attests to the outcome of an event. Additionally, we save the
`nonce_pks` to more easily verify the adaptor signatures.
This should greatly improve resilience as we no longer have any
tasks within `tokio` that can fail without recovering.
Instead, we periodically ping the actor with a `Sync` message which
updates the local state of all scripts and sends out messages accordingly.
This goes towards handling all cfd state transitions in one place, so it becomes easier to reason about it.
Currently, state transitions are scattered over the code of the cfd actor.
This change bundles the actual transition in the cfd itself.
Inserting the new state into the db is still in the responsibility of the caller.
note: the `monitor` import in `taker.rs` should technically not be part of this commit, but was needed because I decided that the `CfdMonitoringEvent` should live in the `monitor` actor. But since that is not part of the `Cfd` in `model` the taker needs to know about the `monitor`.
Daniel Karzel
Philipp Hoenisch
Thomas Eizinger
Lucas Soriano del Pino