Various typespec and compilation improvements

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

lib/mobilizon/events/participant_metadata.ex

@@ -0,0 +1,36 @@
+defmodule Mobilizon.Events.Participant.Metadata do
+  @moduledoc """
+  Participation stats on event
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+  alias Mobilizon.Web.Email.Checker
+
+  @type t :: %__MODULE__{
+          email: String.t(),
+          confirmation_token: String.t(),
+          cancellation_token: String.t(),
+          message: String.t(),
+          locale: String.t()
+        }
+
+  @attrs [:email, :confirmation_token, :cancellation_token, :message, :locale]
+
+  @derive Jason.Encoder
+  embedded_schema do
+    field(:email, :string)
+    field(:confirmation_token, :string)
+    field(:cancellation_token, :string)
+    field(:message, :string)
+    field(:locale, :string)
+  end
+
+  @doc false
+  @spec changeset(t, map) :: Ecto.Changeset.t()
+  def changeset(schema, params) do
+    schema
+    |> cast(params, @attrs)
+    |> Checker.validate_changeset()
+  end
+end