feat: execute service as distributed erlang (#96)

To create a cluster with distributed nodes, the following changes were made:

* Use [`dns_cluster`][0] to execute distributed nodes
* Add _script_ to execute distributed nodes locally

Also, improve local execution by:

* Use [`mix release`][1] to make easier [deploy `phoenix`][2]
* Use [`compose watch`][3] to synchronize code from the host with the service

Some minor improvements:

* Ignore files and folders in git and docker
* Remove boilerplate comments

[0]: https://github.com/phoenixframework/dns_cluster
[1]: https://hexdocs.pm/mix/Mix.Tasks.Release.html
[2]: https://hexdocs.pm/phoenix/releases.html
[3]: https://docs.docker.com/compose/how-tos/file-watch/

Co-authored-by: Joao P Dubas <joao.dubas@gmail.com>
Reviewed-on: #96
Co-authored-by: Joao P Dubas <joao.dubas+gitea@gmail.com>
Co-committed-by: Joao P Dubas <joao.dubas+gitea@gmail.com>

lib/wabanex/application.ex

@@ -1,34 +1,25 @@
 defmodule Wabanex.Application do
-  # See https://hexdocs.pm/elixir/Application.html
-  # for more information on OTP Applications
   @moduledoc false
 
   use Application
 
   def start(_type, _args) do
     children = [
-      # Start the PromEx supervisor
       Wabanex.PromEx,
-      # Start the Ecto repository
       Wabanex.Repo,
-      # Start the Telemetry supervisor
       WabanexWeb.Telemetry,
-      # Start the PubSub system
       {Phoenix.PubSub, name: Wabanex.PubSub},
-      # Start the Endpoint (http/https)
+      {DNSCluster,
+       query: Application.get_env(:wabanex, :dns_cluster_query) || :ignore,
+       log: :info,
+       resolver: Application.get_env(:wabanex, :dns_cluster_resolver) || DNSCluster.Resolver},
       WabanexWeb.Endpoint
-      # Start a worker by calling: Wabanex.Worker.start_link(arg)
-      # {Wabanex.Worker, arg}
     ]
 
-    # See https://hexdocs.pm/elixir/Supervisor.html
-    # for other strategies and supported options
     opts = [strategy: :one_for_one, name: Wabanex.Supervisor]
     Supervisor.start_link(children, opts)
   end
 
-  # Tell Phoenix to update the endpoint configuration
-  # whenever the application is updated.
   def config_change(changed, _new, removed) do
     WabanexWeb.Endpoint.config_change(changed, removed)
     :ok