Remove contact_info from validation process

[nicholaspcr]

Summary

OS counterpart of https://github.com/TheThingsIndustries/lorawan-stack/pull/4012

Changes

• Add migration to create email_validations table
• Add EmailValidationRegistry to api
• Add EmailValidationStore interface to IS's store
• Update webui to call EmailValidationRegistry instead of ContactInfoRegistry when validating emails.

Testing

Unit tests and manual testing.

Test Steps

Use the following configuration for the Stack (remember to swap <field_ref> with an appropriate value):

 tls:
  source: file
  root-ca: ./ca.pem
  certificate: ./cert.pem
  key: ./key.pem
is:
  email:
    provider: "dir"
    dir: <dir_path> # (for example "./.env/emails/")
    sender-address: <sender_address>
    sender-name: <sender_name>
    templates:
      source: "dir"
      directory: "./pkg/email/templates"
  user-registration:
    email-validation:
      required: true
      retry-interval: 1h0m0s
      token-ttl: 48h0m0s

Follow the steps below:

1. Create two users.
2. Check the <dir_path> used in the config to validate if two emails were sent.
3. Select one of the emails and use the link to validate the user's account
4. Select the other email and use the reference and token to validate the account via the CLI.
5. Validate if both users have their emails validated.
   • Can be done via CLI with the command: ttn-lw-cli usr get <usr_id> --primary-email-address --primary-email-address-validated-at

Regressions

N/A

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• The steps/process to test this feature are clearly explained including testing for regressions.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.

[kschiffer]

This broke the email validation. Please check the end to end tests.

[kschiffer]

See above.