Support secp256k1 jwt signatures

[GlassesAndIce]

Preflight Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Problem Description

Telegram recently started using secp256k1 curve (which seems to be a valid choice according to recent changes to jose spec) in their new OIDC provider. This curve is currently not supported by Dex - trying to log in will lead to 500 Internal server error with go-jose errors in logs.

oidc: failed to verify ID Token: failed to verify signature: fetching keys oidc: failed to decode keys: got Content-Type = application/json, but could not unmarshal as JSON: go-jose/go-jose: unsupported elliptic curve 'secp256k1'

Proposed Solution

Similar issue appeared in supabase, proposed solution was to add a separate jwt verifier path for this specific curve.
supabase/auth#2534

Alternatives Considered

No response

Additional Information

No response