Lookup app servers using multiple SRV records

[roback]

Preparation for when we have two datacenters to deploy to.

[roback]

The test failing has nothing to do with this PR :)

  1) Net::SSH supports the ed25519 algorithm
     Failure/Error: expect(Net::SSH::Authentication::ED25519Loader::LOADED).to be(true)
     
       expected true
            got false
     # ./spec/integration/net_ssh_spec.rb:5:in `block (2 levels) in <top (required)>'

[dentarg]

We should make the build green anyway :-) It was 10 months since we last ran the tests here, so I guess we haven't properly locked our dependencies, I think it would be good to do that

[dentarg]

I suspect this change

• net-ssh 4.2.0: https://travis-ci.org/twingly/capistrano-twingly/jobs/318288023 ✅
• net-ssh 5.0.2: https://travis-ci.org/twingly/capistrano-twingly/jobs/436112469 🔴

[roback]

We should make the build green anyway :-)

Done! net-ssh/net-ssh#563 was the cause behind the failure :)

[dentarg]

We also need to require net-ssh >= 5

$ bundle
Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies...
Using bcrypt_pbkdf 1.0.0
Using bundler 1.16.1
Using ed25519 1.2.4
Using net-ssh 4.2.0
Bundle complete! 3 Gemfile dependencies, 4 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

~/Downloads/test
$ bundle exec ruby -e 'require "net/ssh"; p Net::SSH::Authentication::ED25519Loader::LOADED'
false

$ bundle
Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies...
Using bcrypt_pbkdf 1.0.0
Using bundler 1.16.1
Using ed25519 1.2.4
Using net-ssh 5.0.2
Bundle complete! 3 Gemfile dependencies, 4 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

~/Downloads/test
$ bundle exec ruby -e 'require "net/ssh"; p Net::SSH::Authentication::ED25519Loader::LOADED'
true

References:

• [DOC] net-ssh 5 and later ed25519 support net-ssh/net-ssh#565
• [DOC] net-ssh ed25519 support net-ssh/net-ssh#478

[roback]

We also need to require net-ssh >= 5

Ah, yes, of course :)