fix: support more key formats

[cheina97]

Problem

When establishing peering between clusters, the tenant controller fails with the following error:

failed to parse public key: asn1: structure error: tags don't match (16 vs {class:2 tag:29 length:53 isCompound:false})

Cause

The VerifyNonce and checkCSR functions in the authentication module expected public keys to be strictly in PKIX DER-encoded format. An older version of liqoctl was storing the public key in a different format, causing the ASN.1 parser to fail.

Solution

Added a parsePublicKey helper function that attempts to parse the public key from multiple formats:

1. First tries PEM decoding (if the data contains a PEM block)
2. Then tries PKIX DER parsing
3. Falls back to raw Ed25519 public key (32 bytes)

Updated both VerifyNonce and checkCSR functions to use this flexible parsing approach, ensuring backward compatibility with Tenant resources created by older liqoctl versions.

[adamjensenbot]

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