Unify deploy secret keys for the main server

We were using `server` on staging but `server1` and `server2` on
preproduction and production.

The reason behind it is we've always used one server on staging but
sometimes we've used several servers on preproduction and production.

However, this is a bit of a mess on installations which have only one
server on preproduction or production and need to use the `server` key
for the staging environments but `server1` for other environments.

So, in order to keep compatibility with existing Consul installations,
we're now allowing either `server` or `server1` on any environment.

config/deploy-secrets.yml.example

@@ -7,12 +7,12 @@ staging:
 preproduction:
   deploy_to: "/home/deploy/consul"
   ssh_port: "2222"
-  server1: xxx.xxx.xxx.xxx
+  server: xxx.xxx.xxx.xxx
   user: "deploy"
 
 production:
   deploy_to: "/home/deploy/consul"
   ssh_port: "22"
-  server1: xxx.xxx.xxx.xxx
+  server: xxx.xxx.xxx.xxx
   server2: xxx.xxx.xxx.xxx
   user: "deploy"

config/deploy.rb

@@ -3,7 +3,15 @@ lock "~> 3.17.1"
 
 def deploysecret(key)
   @deploy_secrets_yml ||= YAML.load_file("config/deploy-secrets.yml")[fetch(:stage).to_s]
-  @deploy_secrets_yml.fetch(key.to_s, "undefined")
+  @deploy_secrets_yml.fetch(key.to_s, "")
+end
+
+def main_deploy_server
+  if deploysecret(:server1) && !deploysecret(:server1).empty?
+    deploysecret(:server1)
+  else
+    deploysecret(:server)
+  end
 end
 
 set :rails_env, fetch(:stage)

config/deploy/preproduction.rb

@@ -1,3 +1,3 @@
 set :branch, ENV["branch"] || :master
 
-server deploysecret(:server1), user: deploysecret(:user), roles: %w[web app db importer cron background]
+server main_deploy_server, user: deploysecret(:user), roles: %w[web app db importer cron background]

config/deploy/production.rb

@@ -1,6 +1,6 @@
 set :branch, ENV["branch"] || :master
 
-server deploysecret(:server1), user: deploysecret(:user), roles: %w[web app db importer cron background]
+server main_deploy_server, user: deploysecret(:user), roles: %w[web app db importer cron background]
 #server deploysecret(:server2), user: deploysecret(:user), roles: %w(web app db importer cron background)
 #server deploysecret(:server3), user: deploysecret(:user), roles: %w(web app db importer)
 #server deploysecret(:server4), user: deploysecret(:user), roles: %w(web app db importer)

config/deploy/staging.rb

@@ -1,3 +1,3 @@
 set :branch, ENV["branch"] || :master
 
-server deploysecret(:server), user: deploysecret(:user), roles: %w[web app db importer cron background]
+server main_deploy_server, user: deploysecret(:user), roles: %w[web app db importer cron background]