LPv2: ForeignInvestments changes

[lemunozm]

Description

Required changes in pallet-foreign-investments for LPv2

Checkout the sequence diagrams before reviewing this: https://centrifuge.hackmd.io/H4v-SV0zRuCxC29kxoqOgQ

Changes and Descriptions

• Modify decrease by cancel
  • This allows big simplifications if we know that no more increases/decreases can occur from a cancel if request until the Fulfilled cancel msg is sent.
• Remove the no longer used collect_* and investment() and redemption() methods from ForeignInvestment trait.
• Remove the remaining amount from output messages.
• The correlation has been simplified. We no longer need to store both foreign and pool amounts to correlate. We know that the previous correlation.pool_amount always matches to T::Investment::investment() so we only need to store the foreign amount. The correlation is only done in just one point in the code: in post_collect(), so we no longer need a correlation struct to handle any case generically. We can just simplify for the one needed case.
• Swapping calls and hooks are now called in entities.rs, leaving the impl.rs file much more readable.
• Unify hooks into the same new trait ForeignInvestmentHooks
• Remove pallet-swaps
  • We no longer need to apply a swap over an existent inverse swap. From now on we only need to create, increase, and cancel a swap. That means that most valuable parts from pallet-swap are no longer used, so we can just drop that pallet and handle the order-book direclty from foreign-investment again. Also, not having pallet-swaps makes easy the deal with different ratios in opposite swaps.

Blocked by #1892

[lemunozm]

We only used this to know how much we need to cancel, so it is no longer needed

[wischli]

This definitely improves comprehensibility of foreign investments by orders of magnitude 🎉 I have quite an amount of questions.

I will create a branch which combines both our changes in order to continue working on the ITs which need the fulfilled changes on our side.

[wischli]

Makes sense. For other reviewers here's a simple example to put some face to these lines:

Say

• self.foreign_amount = 1000 F
• collected.amount_payment = 100 P
• invested = 400 P --> pool_amount_before_collecting = 500 P

Then collected_foreign_amount = 1000F * 100P / 500P = 200F which makes sense because 1000F = 500P

[lemunozm]

Thanks a lot for your super deep review @wischli!!

I will create a branch which combines both our changes in order to continue working on the ITs which need the fulfilled changes on our side.

Before doing this, if you want, to avoid extra branches, we can

• merge this into your branch
• merge your branch (even with the failing tests) into feat/lp-v2 and later merge this as another PR on that branch.

[wischli]

Thanks a lot for your super deep review @wischli!!

Thanks for answering all my questions so quickly! IMO, this branch can be merged to the feature branch indeed.

I will create a branch which combines both our changes in order to continue working on the ITs which need the fulfilled changes on our side.

Before doing this, if you want, to avoid extra branches, we can

• merge this into your branch
• merge your branch (even with the failing tests) into feat/lp-v2 and later merge this as another PR on that branch.

I would prefer this because I can imagine that fixing all Solidity ITs won't happen in the near future. Especially, if minor Solidity code changes might be required, which could be the case.

[wischli]

I'm fine with merging this into my branch. The few clippy complaints can be fixed by me then.

[lemunozm]

CI for this is still blocked, I'm gonna merge @wischli