Make conversion of Stellar DIA assets unique (bi-directionally)

[ebma]

Right now, the DiaOracleKeyConvertor does not take the issuer of stellar assets into account. We should think about changing that. We should find a way to translate between Stellar assets and DIA identifiers bi-directionally meaning that a Stellar asset (issuer + code) is uniquely defined by a DIA asset and vice versa.
For this to work, we might also have to touch the dia-batching-server implementation because this responds to the prices for DIA assets.

[ebma]

@pendulum-chain/product this is a follow-up ticket of #234.
The motivation for this ticket is to disambiguate the conversion of Stellar assets in the DIA oracle pallet. As it is right now, we only check the code of a Stellar asset and then assign a price to it. E.g. for the GABCD...:USDC Stellar asset, we only check the code which is USDC, and conclude that we should use the USD fiat price. We don't take into account the issuer, however, so the GABCD...:USDC asset will be treated the same as a GDCBA...:USDC asset. While this works, we eventually might want to be able to differentiate between the two. That's what this ticket is about.

[vadaynujra]

Differentiate wrt the price or other factors as well i.e. is the benefit of this disambiguation only to be able to assign separate price feeds or to differentiate between the two assets, in general?

[ebma]

Since this ticket is only about changes regarding the price oracle it's only in regard to separate price feeds.
Imagine that for some USDC we want to assign the FIAT price and for another, we want to assign some blockchain price (ie. the price of USDC on Ethereum). This is not possible right now but would be possible afterward.
Not saying that we want or should do this anytime soon or ever.

[prayagd]

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[prayagd]

@ebma candidate for icebox?

[ebma]

Yes, it's not urgent right now.