Add gems to suport ed25519 keys in capistrano

[vandrijevik]

Release Notes

TECH TASK: Allow using ed25519 keys to deploy via capistrano

Additional Context

Without these gems, capistrano fails with the following message:

$ bundle exec cap staging deploy
(Backtrace restricted to imported tasks)
cap aborted!
NotImplementedError: unsupported key type `ssh-ed25519'
net-ssh requires the following gems for ed25519 support:
 * rbnacl (>= 3.2, < 5.0)
 * rbnacl-libsodium, if your system doesn't have libsodium installed.
 * bcrypt_pbkdf (>= 1.0, < 2.0)
See https://github.com/net-ssh/net-ssh/issues/478 for more information
Gem::LoadError : "rbnacl is not part of the bundle. Add it to your Gemfile."

Tasks: TOP => rvm:hook
(See full trace by running task with --trace)

https://blog.g3rt.nl/upgrade-your-ssh-keys.html is a good overview of Ed25519 SSH keys, and why it’s a good idea to migrate towards using them.

[jhanggi]

Can we get away with require: false in these? And it's still not possible to remove the upper constraint? Looks like that issue was over a year ago.

[vandrijevik]

I’ll try specifying require: false here to see if net-ssh will pick them up correctly. As for the upper version constraint, we can’t get rid of it because even net-ssh 5 (and our bundle is still at 4.2) specifies the same < 2.0 limit: net-ssh/net-ssh#565

[vandrijevik]

@jhanggi require: false worked, so I added it in 4e71fa5 (along with mentioning that the note is for 4.2 of net-ssh)