Add verification to StripeConnectAccount

[joshsmith]

Problem

We'll need to add properties from the verification hash to the StripeConnectAccount.

In particular:

• verification_disabled_reason
• verification_due_by
• verification_fields_needed - can format as a list; in Ecto is an {:array, :string}

Needs:

• migration
• new model tests
• new fields on the model
• change the update changeset

[begedin]

stripity-stripe is going to need to add support for that part of the account payload in beam-community/stripity-stripe#153