Add support for OKP key type validation

[orelmaliach]

As per

strimzi-kafka-oauth/oauth-common/src/main/java/io/strimzi/kafka/oauth/validator/JWTSignatureValidator.java

Lines 396 to 403 in 399a19f

	if (jwk instanceof ECKey) {
	publicKey = ((ECKey) jwk).toPublicKey();
	} else if (jwk instanceof RSAKey) {
	publicKey = ((RSAKey) jwk).toPublicKey();
	} else {
	log.warn("Unsupported JWK key type: {}", jwk.getKeyType());
	continue;
	}

when an auth server returns JWK key whose type is OKP (com.nimbusds.jose.jwk.OctetKeyPair), it's not being added to validator cache, and later kafka fails to authenticate with error:
Failed authentication - Token validation failed: Unknown signing key. Only RSA/EC key types are supported.

Would it be possible to add support for validating JWTs signed with OKP (FIPS-compliant) key type?

[scholzj]

@mstruk Any thoughts on this?

[mstruk]

I need to do a little more research to see if it is as easy as it seems.

[see-quick]

Any news on this @mstruk ?

[mstruk]

I added the comment to the PR: #298

[scholzj]

Triaged on 30.4.2026: From the discussion on #298, it seems like a useful feature, but we need to figure out the right implementation. Marking it as triaged.