Fix some typespecs

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

lib/mobilizon/instances/instance.ex

@@ -7,6 +7,7 @@ defmodule Mobilizon.Instances.Instance do
   use Ecto.Schema
 
   @type t :: %__MODULE__{
+          domain: String.t(),
           event_count: non_neg_integer(),
           person_count: non_neg_integer(),
           group_count: non_neg_integer(),

lib/web/email/mailer.ex

@@ -5,7 +5,7 @@ defmodule Mobilizon.Web.Email.Mailer do
   use Swoosh.Mailer, otp_app: :mobilizon
   alias Mobilizon.Service.ErrorReporting.Sentry
 
-  @spec send_email(Swoosh.Email.t()) :: Swoosh.Email.t()
+  @spec send_email(Swoosh.Email.t()) :: {:ok, term} | {:error, term}
   def send_email(email) do
     Mobilizon.Web.Email.Mailer.deliver(email)
   rescue