Introduce comments below events

Also add tomstones

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

lib/mobilizon/tombstone.ex

@@ -0,0 +1,45 @@
+defmodule Mobilizon.Tombstone do
+  @moduledoc """
+  Represent tombstones for deleted objects. Saves only URI
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Storage.Repo
+
+  @type t :: %__MODULE__{
+          uri: String.t(),
+          actor: Actor.t()
+        }
+
+  @required_attrs [:uri, :actor_id]
+  @optional_attrs []
+  @attrs @required_attrs ++ @optional_attrs
+
+  schema "tombstones" do
+    field(:uri, :string)
+    belongs_to(:actor, Actor)
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(%__MODULE__{} = tombstone, attrs) do
+    tombstone
+    |> cast(attrs, @attrs)
+    |> validate_required(@attrs)
+  end
+
+  @spec create_tombstone(map()) :: {:ok, Ecto.Schema.t()} | {:error, Ecto.Changeset.t()}
+  def create_tombstone(attrs) do
+    %__MODULE__{}
+    |> changeset(attrs)
+    |> Repo.insert(on_conflict: :replace_all, conflict_target: :uri)
+  end
+
+  @spec find_tombstone(String.t()) :: Ecto.Schema.t() | nil
+  def find_tombstone(uri) do
+    Repo.get_by(__MODULE__, uri: uri)
+  end
+end