Hash PII info in a storable hash for us to check against for MPI consistency

[bosawt]

Here's how it might go:

• Initial IAL2 login from login.gov, we have eauth headers with PII
• Hash Name, Birth-date, SSN, store this in Account table or whatever analogy we're using. Mapping is now login_gov_uuid -> icn and pii_hash
• Future IAL1 logins prove they've been verified before, so we look up login_gov_uuid, retrieve icn, and make MPI call
• We hash the PII from MPI call and compare to the pii_hash value
  *If it matches, user is authed at IAL2 Level
• If it does not match, user is upleveled to IAL2 through standard auth flow, we store new values for icn and pii_hash