Deprecate c_rehash and multi certificate bundle handling
Summary
GitLab Omnibus used OpenSSLs c_rehash to prepare custom certificate authorities.
OpenSSL still bundles c_rehash but recommends to use openssl rehash instead, which is a built-in command not relying on perl being installed.
In %18.2 we switched to !8306 (merged) for all supported distros but AmazonLinux 2 (which does not have c_rehash yet).
We had to relax this behavior in !8711 (merged) because openssl rehash does not handle certificate bundles with multiple certificates.
Proposal
- Announce deprecation of support for certificate bundles with multiple certificates. (Suggestion: Target the same milestone as Announce AmazonLinux 2 deprecation (#8845)).
- In the removal milestone, drop the c_rehash fallback and error out if a certificate with multiple bundles is detected.