The proxy used to boot with no master key (every request accepted without
authentication) and with sk-1234, the key every example used. It now stops at
startup, before it connects to the database, and prints how to fix it: where the
bad key came from, a copy-pastable command that generates a secure key, and,
when the public key is also encrypting a database, a link to the rotation guide
general_settings.dangerously_allow_unsafe_proxy: true or
LITELLM_DANGEROUSLY_ALLOW_UNSAFE_PROXY=true starts the proxy anyway, for local
development. CI and test boots that rely on sk-1234 or on no key set it
BREAKING CHANGE: deployments with no master key, an empty one, or sk-1234 no
longer start until they set a real key or opt in to the override
