account
The Stellar account ID extracted from the sub claim.
Handles both standard accounts (G...) and muxed accounts (M...). If the subject contains a memo (format: "ACCOUNT:MEMO"), only the account part is returned.
Example:
sub = "GACCOUNT..."→account = "GACCOUNT..."sub = "GACCOUNT...:12345"→account = "GACCOUNT..."sub = "MACCOUNT..."→account = "MACCOUNT..."
Return
The account ID, or null if sub is not present