Introduce admin and moderator role, check role on list_users action

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Add test for guards

priv/repo/migrations/20190307125009_move_user_role_to_enum.exs

@@ -0,0 +1,41 @@
+defmodule Mobilizon.Repo.Migrations.MoveUserRoleToEnum do
+  use Ecto.Migration
+
+  alias Mobilizon.Users.UserRoleEnum
+
+  def up do
+    UserRoleEnum.create_type()
+
+    alter table(:users) do
+      add(:role_tmp, UserRoleEnum.type(), default: "user")
+    end
+
+    execute("UPDATE users set role_tmp = 'user' where role = 0")
+    execute("UPDATE users set role_tmp = 'moderator' where role = 1")
+    execute("UPDATE users set role_tmp = 'administrator' where role = 2")
+
+    alter table(:users) do
+      remove(:role)
+    end
+
+    rename(table(:users), :role_tmp, to: :role)
+  end
+
+  def down do
+    alter table(:users) do
+      add(:role_tmp, :integer, default: 0)
+    end
+
+    execute("UPDATE users set role_tmp = 0 where role = 'user'")
+    execute("UPDATE users set role_tmp = 1 where role = 'moderator'")
+    execute("UPDATE users set role_tmp = 2 where role = 'administrator'")
+
+    alter table(:users) do
+      remove(:role)
+    end
+
+    UserRoleEnum.drop_type()
+
+    rename(table(:users), :role_tmp, to: :role)
+  end
+end