Contract whitelisted borrowers

[captainrandom]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  It white lists borrows based on a list of addresses stored in a contract. This gets the abi from etherscan.

• What is the current behavior? (You can also link to an open issue here)
  I don't think that there is one? Currently there is a static allowed list, but I'd like to make the borrow white list to be dynamic whenever someone updates the contract (without the need to update the signal).

• What is the new behavior (if this is a feature change)?
  Gets the whitellisted borrower addresses from the smart contract and checks if the provided borrower address is in the set.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

It shouldn't.

• Other information:

[height]

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