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>

config/runtime.exs

@@ -1,5 +1,35 @@
 import Config
 
+# [warn] Conditional IPv6 support missing from runtime configuration.
+#
+# Add the following to your config/runtime.exs:
+#
+#     maybe_ipv6 = if System.get_env("ECTO_IPV6") in ~w(true 1), do: [:inet6], else: []
+#
+#     config :wabanex, Wabanex.Repo,
+#       ...,
+#       socket_options: maybe_ipv6
+#
+# [warn] Conditional server startup is missing from runtime configuration.
+#
+# Add the following to the top of your config/runtime.exs:
+#
+#     if System.get_env("PHX_SERVER") do
+#       config :wabanex, WabanexWeb.Endpoint, server: true
+#     end
+#
+# [warn] Environment based URL export is missing from runtime configuration.
+#
+# Add the following to your config/runtime.exs:
+#
+#     host = System.get_env("PHX_HOST") || "example.com"
+#
+#     config :wabanex, WabanexWeb.Endpoint,
+#       ...,
+#       url: [host: host, port: 443]
+
+config :wabanex, dns_cluster_query: System.get_env("DNS_CLUSTER_QUERY") || :ignore
+
 config :wabanex, Wabanex.Repo,
   username: System.get_env("POSTGRES_USER") || "postgres",
   password: System.get_env("POSTGRES_PASS") || "postgres",