GHSA-7fqc-p256-7pwj: Steeltoe's static JWKS cache shared across schemes and never invalidated

Summary The JWT signing key cache in TokenKeyResolver uses kid as the sole cache key without namespacing by authority. In applications with multiple JwtBearer schemes pointing to different identity providers, a key fetched for one scheme can satisfy token validation for another. Additionally, cached keys have no expiration, so rotated or revoked keys remain trusted until the application process restarts. Impact In multi-scheme deployments, an attacker who controls one identity provider's signing key can forge tokens accepted by other schemes within the same application. For all applications using TokenKeyResolver, a signing key removed from the identity provider's JWKS endpoint remains trusted indefinitely. Mitigations If an immediate upgrade is not possible: - In multi-scheme deployments, configure only one JwtBearer scheme per application when different identity providers are required. - Restart the application process after an identity provider signing key rotation to clear stale cached keys.