Tests whether the Digital Credentials API works from this origin.
org-iso-mdoc protocol per ISO 18013-7 Annex C. Requires iOS 26+ with Developer Integrator profile or real mDL + Apple Business Connect cert.openid4vp-v1-unsigned protocol. Requires Android with Google Wallet sandbox + test ID, or real mDL.Paste a base64url-encoded response string to decode it, or responses from Step 2 will auto-decode above.