Remove PIN and Biometric keys if not added during login

[theblockstalk]

if the user does not add a bin or biometric key during login, we want to be able to update the pin and biometric key so they cannot be used

DOD

• during updateKeys() if pin or biometric keys do not exist (are null) and the blockchain key for pin/biometric is not already null, they are updated on blockchain as eosio.null to make them unusable

// UPDATE
// if pin/biometric is null, and blockchain key !== null, then update blockchain key to = `eosio.null`
user.updateKeys()

• integration test to check if user object pin === null, and blockchain pin !== null, then blockchain pin is set to null
• integration test to check if user object pin === null, and blockchain pin === null, then blockchain pin is not updated
• integration test to check if user object biometric === null, and blockchain biometric !== null, then blockchain pin is set to null
• integration test to check if user object biometric === null, and blockchain biometric === null, then blockchain pin is not updated

Hint:

• check if we can replace keys with a null/generic invalid key option
  https://t.me/antelopedevs/235117