feat: configure dnscluster to allow multi-node

* Configure `docker-compose` to scale at least 2 nodes.
* Add script to start service with proper naming
* Create custom resolver.
  * This is not strictly necessary.

lib/wabanex/application.ex

@@ -15,6 +15,10 @@ defmodule Wabanex.Application do
       WabanexWeb.Telemetry,
       # Start the PubSub system
       {Phoenix.PubSub, name: Wabanex.PubSub},
+      {DNSCluster,
+       query: Application.get_env(:wabanex, :dns_cluster_query) || :ignore,
+       log: :info,
+       resolver: Application.get_env(:wabanex, :dns_cluster_resolver) || DNSCluster.Resolver},
       # Start the Endpoint (http/https)
       WabanexWeb.Endpoint
       # Start a worker by calling: Wabanex.Worker.start_link(arg)

lib/wabanex/dev_dns_cluster_resolver.ex

@@ -0,0 +1,26 @@
+defmodule Wabanex.DevDNSClusterResolver do
+  @moduledoc """
+  Local DNS resolver for cluster query.
+  """
+  require Record
+
+  Record.defrecord(:hostent, Record.extract(:hostent, from_lib: "kernel/include/inet.hrl"))
+
+  def basename(node_name) when is_atom(node_name) do
+    [basename, _] = node_name |> to_string() |> String.split("@")
+    basename
+  end
+
+  def connect_node(node_name) when is_atom(node_name) do
+    Node.connect(node_name)
+  end
+
+  def list_nodes, do: Node.list(:visible)
+
+  def lookup(query, type) when is_binary(query) and type in [:a, :aaaa] do
+    case :inet_res.getbyname(~c"#{query}", type) do
+      {:ok, hostent(h_addr_list: addr_list)} -> addr_list
+      {:error, _} -> []
+    end
+  end
+end