Store id instead of encoded raw_id on external_id column

[joaquintomas2003]

This will make it easier to stop using webauthn-json.

With webauthn-json the create() method expects createOptions of type JSON. However, for using the browser's native API, the create() call must receive the options in type CredentialCreationOptions.

To pass from JSON to CredentialCreationOptions the method parseRequestOptionsFromJSON is used.
parseRequestOptionsFromJSON in turn, expects to receive this format: https://www.w3.org/TR/webauthn-3/#dictdef-publickeycredentialcreationoptionsjson

Therefore, the credential ids inside excludeCredentials need to be of type Base64URLString, which is not the case now.
As of now, the raw_id is being strict encoded which still doesn't comply with being of type Base64URLString.

With this PR, instead of strictly encoding the raw_id, the id attribute starts being stored.
The id is a base64url encoded version of PublicKeyCredential.rawId.

Related discussion:

• Remove webauthn-json #31 (comment)

[santiagorodriguez96]

LGTM