[Payments] Proof of number verification on server side

[AlexBHarley]

Now that we've cut the scope of this project to only include phone numbers in the KYC data, we need a way on the server side to verify the from address of a transfer is mapped to the phone number provided in the KYC data.

• [ ] Get Identifier from ODIS https://docs.celo.org/developer-guide/contractkit/odis
• [ ] Check onchain for existence of phone number mapping in attestation service

[nicolasbrugneaux]

note to self: https://docs.celo.org/developer-guide/contractkit/odis - use this to find out info about the phone number