refactor(media): use UUID instead of ID for media retrieval in GraphQL

Fixes #1760

lib/mobilizon/events/event.ex

@@ -258,9 +258,14 @@ defmodule Mobilizon.Events.Event do
 
   # In case the provided picture is an existing one
   @spec put_picture(Changeset.t(), map) :: Changeset.t()
-  defp put_picture(%Changeset{} = changeset, %{picture: %{media_id: id} = _picture}) do
-    %Media{} = picture = Medias.get_media!(id)
-    put_assoc(changeset, :picture, picture)
+  defp put_picture(%Changeset{} = changeset, %{picture: %{media_uuid: uuid} = _picture}) do
+    case Medias.get_media_by_uuid(uuid) do
+      %Media{} = picture ->
+        put_assoc(changeset, :picture, picture)
+
+      nil ->
+        add_error(changeset, :picture, "Media with UUID #{uuid} not found")
+    end
   end
 
   # In case it's a new picture

lib/mobilizon/medias/media.ex

@@ -5,7 +5,7 @@ defmodule Mobilizon.Medias.Media do
 
   use Ecto.Schema
 
-  import Ecto.Changeset, only: [cast: 3, cast_embed: 2]
+  import Ecto.Changeset
 
   alias Mobilizon.Actors.Actor
   alias Mobilizon.Discussions.Comment
@@ -15,14 +15,19 @@ defmodule Mobilizon.Medias.Media do
   alias Mobilizon.Posts.Post
 
   @type t :: %__MODULE__{
+          uuid: Ecto.UUID.t(),
           file: File.t(),
           metadata: Metadata.t(),
           actor: Actor.t()
         }
 
-  @attrs [:actor_id]
+  @attrs [:actor_id, :uuid]
 
   schema "medias" do
+    # We need read_after_writes because the uuid is generated by
+    # the database gen_random_uuid() function
+    field(:uuid, Ecto.UUID, read_after_writes: true)
+
     embeds_one(:file, File, on_replace: :update)
 
     embeds_one(:metadata, Metadata, on_replace: :update)
@@ -44,5 +49,6 @@ defmodule Mobilizon.Medias.Media do
     |> cast(attrs, @attrs)
     |> cast_embed(:file)
     |> cast_embed(:metadata)
+    |> unique_constraint(:uuid)
   end
 end

lib/mobilizon/medias/medias.ex

@@ -29,6 +29,12 @@ defmodule Mobilizon.Medias do
   @spec get_media!(integer | String.t()) :: Media.t()
   def get_media!(id), do: Repo.get!(Media, id)
 
+  @doc """
+  Get a single media by uuid.
+  """
+  @spec get_media_by_uuid(String.t()) :: Media.t() | nil
+  def get_media_by_uuid(uuid), do: Repo.get_by(Media, uuid: uuid)
+
   @doc """
   Get a media by its URL.
   """