Charm does not allow a user to use specific TLS cipher suites supported by vault

[Marcin Wilk]

The vault application supports 'tls_cipher_suites' tcp listener config option [1] that allows an administrator to specify explicitly which cipher suites should be used. This allows to eliminate weaker, vulnerable suites (ie. those with DES/3DES which are still supported by vault/golang [2]).
It might be useful to expose 'tls_cipher_suites' configuration parameter via charm config option allowing a charm user to provide an explicit list of the suites he wants.
The same may apply to other tcp listener options, ie: 'tls_prefer_server_cipher_suites'[3] or 'tls_min_version'[4].

[1] https://developer.hashicorp.com/vault/docs/configuration/listener/tcp#tls_cipher_suites
[2] https://go.dev/src/crypto/tls/cipher_suites.go
[3] https://developer.hashicorp.com/vault/docs/configuration/listener/tcp#tls_prefer_server_cipher_suites
[4] https://developer.hashicorp.com/vault/docs/configuration/listener/tcp#tls_min_version