Extra containing an array of Android.Nfc.NdefMessage present on the discovered tag.
This extra is mandatory for NfcAdapter.ActionNdefDiscovered intents, and optional for NfcAdapter.ActionTechDiscovered, and NfcAdapter.ActionTagDiscovered intents.
When this extra is present there will always be at least one Android.Nfc.NdefMessage element. Most NDEF tags have only one NDEF message, but we use an array for future compatibility.