Export participants to different formats

* CSV
* PDF (requires Python dependency `weasyprint`)
* ODS (requires Python dependency `pyexcel_ods3`)

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

test/service/export/participants/csv_test.exs

@@ -0,0 +1,22 @@
+defmodule Mobilizon.Service.Export.Participants.CSVTest do
+  use Mobilizon.DataCase
+
+  import Mobilizon.Factory
+
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Service.Export.Participants.CSV
+
+  describe "export event participants to csv" do
+    test "export basic infos" do
+      %Event{} = event = insert(:event)
+      insert(:participant, event: event, role: :creator)
+      insert(:participant, event: event, role: :participant)
+      insert(:participant, event: event, role: :not_approved)
+
+      assert CSV.ready?()
+      assert {:ok, path} = CSV.export(event)
+      assert content = File.read!("uploads/exports/csv/" <> path)
+      assert content =~ "Participant name,Participant status,Participant message"
+    end
+  end
+end