Add 5 tests for JWT allowed_connection_types enforcement which the
authenticator does not yet implement. Two tests (reject MQTT-only for
STANDARD context, reject unknown-only types) fail on assertions because
JwtAuthenticator currently ignores the claim. Three tests (allow
STANDARD, allow with unknown mixed in, case-insensitive match) pass
trivially since the field is not checked.
Also adds ConnectionType property to ClientAuthContext (defaults to
"STANDARD") so the tests compile.
Implement NatsJwt static class with Ed25519 signature verification,
base64url decoding, and JWT parsing. Add UserClaims and AccountClaims
with all NATS-specific fields (permissions, bearer tokens, limits,
signing keys, revocations). Includes 44 tests covering decode, verify,
nonce verification, and full round-trip signing with real NKey keypairs.
Adds the IAccountResolver interface (FetchAsync, StoreAsync, IsReadOnly)
and a MemAccountResolver backed by ConcurrentDictionary for in-memory
JWT storage in tests and simple operator deployments.
Reference: golang/nats-server/server/accounts.go:4035+
- Make ConnectReceived thread-safe with Volatile.Read/Write (accessed from auth timeout task and command pipeline)
- Include authTimeoutTask in Task.WhenAny to propagate exceptions
- Clear nonce after authentication with CryptographicOperations.ZeroMemory
- Avoid closure allocation on publish permission cache hot path (method group)
- Update AuthTimeout default to 2s to match Go server
