Fully implement "stateless" logic

[astroseger]

We should modify state_service in order to full implement state-less logic described here: https://github.com/singnet/dev-portal/blob/master/docs/concepts/mpe-stateless-client.md

[astroseger]

I've removed my initial proposition of simplified state_service because it was obviously wrong, so we should implement the design which is written in https://github.com/singnet/dev-portal/blob/master/docs/concepts/mpe-stateless-client.md

It means that we simple should add two new fields:

• oldnonce_signed_amount last amount which was signed by client with nonce=current_nonce - 1.
• oldnonce_signature - last signature sent by client with nonce = current_nonce - 1.

it is still very simple...

[astroseger]

@raamb
Could we prioritize this issue? We cannot properly make SDK without it.

[astroseger]

@Dinesh2521
I would also propose to change authorization strategy, similar to control_service (include block_number in the message to sign).

[astroseger]

There are two issues with the current implementation (#232):

1. It is not backward compatible, and as I believe it is possible to do it backward compatible
2. If current_signed_amount is 0 then daemon doesn't send old_nonce_signed_amount even if it is not 0.

It should be noted that we need old_nonce_signed_amount field only when last payment hasn't been claimed in the MPE contract (channel_nonce != block_chain_nonce). Daemon removes payments from the payment storage after it verify that nonce in blockchain has been updated.

It means that we could take old_nonce_signed_amount directly from payment storage. If there is no payment in payment storage for the given channel_id then we shouldn't send old_nonce_signed_amount (because we know that client will not need it anyway).

[vsbogd]

Taking into account data incompatibility, I would propose to revert last PR and rethink implementation, @Dinesh2521, @raamb , what do you think?

[raamb]

I agree. @Dinesh2521 please revert this PR from main. Once the fixes have been made we can create a new PR