Add method to verify OTP received via email

[alexesprit]

Changes

This PR adds a new method to verify OTP received via email.

References

Should resolve #148.

Testing

const client = new AuthenticationClient({
  domain: "your_domain",
  clientId: "your_client_id",
})

await client.requestEmailCode({
  email: "mail@example.com",
})

// Wait for OTP

await client.verifyEmailCode({
  email: "mail@example.com",
  otp: "123456"
})

I added tests for this method as well.

• This change adds unit test coverage
• This change adds integration test coverage

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors

[davidpatrick]

Looks good thanks for the PR, just some small requested changes.

[alexesprit]

Thank you for the review!

I've pushed changes you requested; also I removed one of test cases, as it became invalid.

[davidpatrick]

Thanks 🙇