* openAPI: StorageRequestCreation: reward => pricePerByte, collateral => collateralPerByte
* purchasing: reward => pricePerByte, collateral => collateralPerByte
* Updates availabilities and reservations to use totalCollateral, minPricePerByte, and maxCollateralPerByte
* Uses correct div operator when operating on UInt256
* proposal updating totalCollateral in availability
* makes sure that reading currentCollateral happens before freeing slot
* Updates naming
* fixes tests: unit and contracts
* uses feat/price-per-byte branch for codex-contracts-eth
* temporarily disables integration tests on CI
* introduces high level <<totalCollateral>> property for a cleaner external interface
* updates integration tests
* Applies review comments
* Updates description of totalCollateral in SalesAvailability
* updates codex-contracts-eth (price-per-byte)
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