Various typespec and compilation improvements

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

lib/web/email/mailer.ex

@@ -5,6 +5,7 @@ defmodule Mobilizon.Web.Email.Mailer do
   use Bamboo.Mailer, otp_app: :mobilizon
   alias Mobilizon.Service.ErrorReporting.Sentry
 
+  @spec send_email_later(Bamboo.Email.t()) :: Bamboo.Email.t()
   def send_email_later(email) do
     Mobilizon.Web.Email.Mailer.deliver_later!(email)
   rescue
@@ -17,6 +18,7 @@ defmodule Mobilizon.Web.Email.Mailer do
       reraise error, __STACKTRACE__
   end
 
+  @spec send_email(Bamboo.Email.t()) :: Bamboo.Email.t() | {Bamboo.Email.t(), any()}
   def send_email(email) do
     Mobilizon.Web.Email.Mailer.deliver_now!(email)
   rescue