Add reminder to expose second factors in a collection.
Change locales to include country code.

This prevents ambiguity when selecting e-mail templates, which are
indexed by language code and country code (ISO 639-1 +
ISO 3166-1 alpha-2) joined with an underscore (e.g. en_GB).
Add commonName, email, verificationCode and nonce to possession events
Move Mockery to development dependencies.
Add email verification code nonce and email verified status on unverified second factor read model.
Add docblock to API SecondFactorRepository#proveYubikeyPossession().
Send e-mail verification e-mail after second factor verification.