Send "Ready to verify" email when IPP enrollment is created

[aduth]

Why: As a public user trying to proof online I want to see the details of my newly scheduled in-person proofing visit to the USPS as an email so that I can reference it later.

Testing Instructions:

1. Navigate to http://localhost:3000
2. Sign in
3. Navigate to http://localhost:3000/verify
4. Complete proofing process up to document capture
5. Use attention result test YAML file for field upload
6. Click "Submit"
7. On warning screen, opt to verify in person
8. Complete proofing process up to "You're ready to verify in person"
9. Navigate to http://localhost:1080
10. Observe there is an email message with details of in-person verification

Screenshot:

Implementation notes:

• Currently, this is only implemented in the PasswordConfirmController version of this flow, not Idv::ReviewController (see related Slack thread). I'll update this pull request if necessary enrollment creation is merged before this one.

Open questions:

• This sends the email at the same time as the enrollment is created in USPS' system, which occurs at password creation. From a UX perspective, this is before the user has finished the personal key confirmation, though this step is technically optional (the user has a profile and the USPS enrollment record is created regardless if they complete personal key step).

[tomas-nava]

approve!