POL BNT -> ETH conversion

[ivanzhelyazkov]

• Add BNT -> ETH trades to POL contract using a dutch auction:
  Based on this Protocol Owned ETH Spending Proposition
• Add tests
• Add deployment scripts

[lbeder]

I think this should've been simpler to implement in a separate CarbonPOL-like contract, while sharing some functionality with the original CarbonPOL contract via a library. It will prevent some of the side effects and "double meaning".

Let's discuss and then I'll continue my review 🙏

[ivanzhelyazkov]

I think this should've been simpler to implement in a separate CarbonPOL-like contract, while sharing some functionality with the original CarbonPOL contract via a library. It will prevent some of the side effects and "double meaning".

Let's discuss and then I'll continue my review 🙏

I think that for the time being this should be sufficient - I realize there are some inconsistencies, this is why I wanted to split the logic in buy and sell - different prices, trade start times and trade functions.
But given that a new integration would be required and the technical time for that, and that we're only adding ETH->BNT trades, it's easier to keep the current interface with no changes (much simpler to integrate) .

[yudilevi]

Yup, definitely much better :)