WebAuthn have updated their specification to set the maximum size of the
CredentialID to 1023 bytes. This is somewhat larger than our current
size and therefore we need to migrate.
The PR changes the struct to add CredentialIDBytes and migrates the CredentialID string
to the bytes field before another migration drops the old CredentialID field. Another migration
renames this field back.
Fix#20457
- Switch to use `CryptoRandomBytes` instead of `CryptoRandomString`, OAuth's secrets are copied pasted and don't need to avoid dubious characters etc.
- `CryptoRandomBytes` gives  `CryptoRandomString` gives  possible states.
- Add a prefix, such that code scanners can easily grep these in source code.
- 32 Bytes + prefix
Migrate from U2F to Webauthn
Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>