Issue 333 don't allow sites starting with beacon

lib/beacon/types/site.ex

@@ -36,6 +36,14 @@ defmodule Beacon.Types.Site do
 
   def valid?(_site), do: false
 
+  def valid_name?(site) when is_atom(site) do
+    valid_name?(Atom.to_string(site))
+  end
+
+  def valid_name?(site) when is_binary(site) do
+    not String.starts_with?(site, "beacon_")
+  end
+
   @doc false
   def safe_to_atom(site) when is_atom(site), do: site
   def safe_to_atom(site) when is_binary(site), do: String.to_existing_atom(site)

lib/mix/tasks/install.ex

@@ -338,6 +338,7 @@ defmodule Mix.Tasks.Beacon.Install do
 
     cond do
       !Beacon.Types.Site.valid?(site) -> raise_with_help!("Invalid site name. It should not contain special characters.")
+      !Beacon.Types.Site.valid_name?(site) -> raise_with_help!("Invalid site name. The site name can't start with \"beacon_\".")
       :default -> options
     end
   end

test/beacon/types/site_test.exs

@@ -24,4 +24,14 @@ defmodule Beacon.Types.SiteTest do
     assert Site.load("site") == {:ok, :site}
     assert Site.load(0) == :error
   end
+
+  describe "valid_name?/1" do
+    test "SUCCESS: Return TRUE if it is a valid name" do
+      assert Site.valid_name?("some_name")
+    end
+
+    test "SUCCESS: Return FALSE if it is an invalid name" do
+      refute Site.valid_name?("beacon_some_name")
+    end
+  end
 end

test/mix/tasks/install_test.exs

@@ -443,6 +443,11 @@ defmodule Mix.Tasks.Beacon.InstallTest do
         Install.run(["--site", "my@site!"])
       end
 
+      # Invalid site name
+      assert_raise Mix.Error, fn ->
+        Install.run(["--site", "beacon_"])
+      end
+
       # Invalid option
       assert_raise OptionParser.ParseError, ~r/1 error found!\n--invalid-argument : Unknown option/, fn ->
         Install.run(["--invalid-argument", "invalid"])