GHSA-jjhc-v7c2-5hh6: LiteLLM: Authentication bypass via OIDC userinfo cache key collision

LiteLLM had a security flaw where JWT authentication (a method to verify user identity using encoded tokens) could be bypassed through a cache key collision. When JWT authentication was enabled, the system only used the first 20 characters of a token as a cache key, and since different tokens from the same signing algorithm could have identical first 20 characters, an attacker could create a fake token matching a legitimate user's cached token and gain their permissions. The flaw only affects deployments with JWT/OIDC authentication explicitly enabled, which is not the default configuration.