When using mutual TLS, you must specify the CA certificate chain to use
for verifying the peer. Using Puma's `ssl_bind` DSL did not give you the
option of doing so, which lead to confusing errors when attempting to
use it.
Now, when specifying the `verify_mode` as either `peer` or `force_peer`,
you can use the DSL to set the `ca` value as needed within the `Binder`.
This allows you to use the DSL instead of falling back to the default
`bind` syntax via the URI-style configuration pattern.