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
Unfortunately credentialIDs in u2f are 255 bytes long which with base32 encoding
becomes 408 bytes. The default size of a xorm string field is only a VARCHAR(255)
This problem is not apparent on SQLite because strings get mapped to TEXT there.
Fix#18727
zeripath