Refactor Core things, including Ecto handling, ActivityPub & Transmogrifier modules

* Data doesn't need anymore to be converted to ActivityStream format to
be saved (this was taken from Pleroma and not at all a good idea here)
* Everything saved when creating an event is inserted into PostgreSQL in
a single transaction

priv/repo/migrations/20191022083446_add_eager_materialized_view_for_searching_events.exs

@@ -1,12 +1,5 @@
 defmodule Mobilizon.Storage.Repo.Migrations.AddEagerMaterializedViewForSearchingEvents do
   use Ecto.Migration
-  import Ecto.Query
-
-  alias Mobilizon.Storage.Repo
-  alias Mobilizon.Service.Search
-  alias Mobilizon.Events.Event
-
-  require Logger
 
   def up do
     create table(:event_search, primary_key: false) do
@@ -28,35 +21,6 @@ defmodule Mobilizon.Storage.Repo.Migrations.AddEagerMaterializedViewForSearching
 
     # to support updating CONCURRENTLY
     create(unique_index("event_search", [:id]))
-
-    flush()
-
-    events =
-      Event
-      |> preload([e], :tags)
-      |> Repo.all()
-
-    nb_events = length(events)
-
-    IO.puts("\nStarting setting up search for #{nb_events} events, this can take a while…\n")
-    insert_search_event(events, nb_events)
-  end
-
-  defp insert_search_event([%Event{url: url} = event | events], nb_events) do
-    with {:ok, _} <- Search.insert_search_event(event) do
-      Logger.debug("Added event #{url} to the search")
-    else
-      {:error, res} ->
-        Logger.error("Error while adding event #{url} to the search: #{inspect(res)}")
-    end
-
-    ProgressBar.render(nb_events - length(events), nb_events)
-
-    insert_search_event(events, nb_events)
-  end
-
-  defp insert_search_event([], nb_events) do
-    IO.puts("\nFinished setting up search for #{nb_events} events!\n")
   end
 
   def down do

priv/repo/migrations/20191023143659_move_participants_stats_to_event.exs

@@ -0,0 +1,15 @@
+defmodule Mobilizon.Storage.Repo.Migrations.MoveParticipantsStatsToEvent do
+  use Ecto.Migration
+
+  def up do
+    alter table(:events) do
+      add(:participant_stats, :map)
+    end
+  end
+
+  def down do
+    alter table(:events) do
+      remove(:participant_stats)
+    end
+  end
+end

priv/repo/migrations/20191024204726_add_tags_to_comments.exs

@@ -0,0 +1,14 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddTagsToComments do
+  use Ecto.Migration
+
+  def up do
+    create table(:comments_tags, primary_key: false) do
+      add(:comment_id, references(:comments, on_delete: :delete_all), primary_key: true)
+      add(:tag_id, references(:tags, on_delete: :nilify_all), primary_key: true)
+    end
+  end
+
+  def down do
+    drop(table(:comments_tags))
+  end
+end

priv/repo/migrations/20191025083642_add_mention_tables.exs

@@ -0,0 +1,16 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddMentionTables do
+  use Ecto.Migration
+
+  def change do
+    create table(:mentions) do
+      add(:silent, :boolean, default: false, null: false)
+      add(:actor_id, references(:actors, on_delete: :delete_all), null: false)
+      add(:event_id, references(:events, on_delete: :delete_all), null: true)
+      add(:comment_id, references(:comments, on_delete: :delete_all), null: true)
+
+      timestamps()
+    end
+
+    create(index(:mentions, [:actor_id]))
+  end
+end

priv/repo/migrations/20191025115537_add_unique_index_on_ur_ls.exs

@@ -0,0 +1,8 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddUniqueIndexOnURLs do
+  use Ecto.Migration
+
+  def change do
+    create(unique_index(:events, [:url]))
+    create(unique_index(:comments, [:url]))
+  end
+end