Introduce the group activity section

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

priv/repo/migrations/20210217164549_add_member_since_to_members.exs

@@ -0,0 +1,34 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddMemberSinceToMembers do
+  use Ecto.Migration
+
+  def up do
+    alter table(:members) do
+      add(:member_since, :utc_datetime)
+    end
+
+    flush()
+
+    %Postgrex.Result{rows: rows} =
+      Ecto.Adapters.SQL.query!(
+        Mobilizon.Storage.Repo,
+        "SELECT id, role FROM members"
+      )
+
+    Enum.each(rows, fn [id, role] ->
+      if role in ["member", "moderator", "administrator", "creator"] do
+        Ecto.Adapters.SQL.query!(
+          Mobilizon.Storage.Repo,
+          "UPDATE members SET member_since = '#{DateTime.to_iso8601(DateTime.utc_now())}' WHERE id = '#{
+            Ecto.UUID.cast!(id)
+          }'"
+        )
+      end
+    end)
+  end
+
+  def down do
+    alter table(:members) do
+      remove(:member_since)
+    end
+  end
+end