Object / Person identification using SDM NFC cards

At Teckids, we want to identify persons using SUN/SDM-capable NFC tags (NTAG 424 DNA). For this, we need the following:

• A stable object identifier URI endpoint (in Core)
  • Using modular authenticators, cf. core issue
• An nfc__sdm_master_key preference, defaulting to 16 byts of binary 0 (NUL)
• A last_read_counter field to store the last seen read counter value
• An ObjectAuthenticator to verify the URL parameters cryptographically
• Support for a "printer" to write URLs to cards
  • With possibility for interactive two-step printing: FIrst, print graphics to cards; second, batch-write URLs to cards using a separate NFC writer station