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

test/mobilizon/actors/actors_test.exs

@@ -99,7 +99,7 @@ defmodule Mobilizon.ActorsTest do
            preferred_username: preferred_username,
            domain: domain,
            avatar: %FileModel{name: picture_name} = _picture
-         } = _actor} = ActivityPub.get_or_fetch_by_url(@remote_account_url)
+         } = _actor} = ActivityPub.get_or_fetch_actor_by_url(@remote_account_url)
 
         assert picture_name == "avatar"
 
@@ -149,7 +149,7 @@ defmodule Mobilizon.ActorsTest do
 
     test "get_actor_by_name_with_preload!/1 returns the remote actor with its organized events" do
       use_cassette "actors/remote_actor_mastodon_tcit" do
-        with {:ok, %Actor{} = actor} <- ActivityPub.get_or_fetch_by_url(@remote_account_url) do
+        with {:ok, %Actor{} = actor} <- ActivityPub.get_or_fetch_actor_by_url(@remote_account_url) do
           assert Actors.get_actor_by_name_with_preload(
                    "#{actor.preferred_username}@#{actor.domain}"
                  ).organized_events == []
@@ -178,7 +178,8 @@ defmodule Mobilizon.ActorsTest do
     test "test build_actors_by_username_or_name_page/4 returns actors with similar usernames",
          %{actor: %Actor{id: actor_id}} do
       use_cassette "actors/remote_actor_mastodon_tcit" do
-        with {:ok, %Actor{id: actor2_id}} <- ActivityPub.get_or_fetch_by_url(@remote_account_url) do
+        with {:ok, %Actor{id: actor2_id}} <-
+               ActivityPub.get_or_fetch_actor_by_url(@remote_account_url) do
           %Page{total: 2, elements: actors} =
             Actors.build_actors_by_username_or_name_page("tcit", [:Person])
 
@@ -253,12 +254,11 @@ defmodule Mobilizon.ActorsTest do
       }
 
       {:ok, data} = MobilizonWeb.Upload.store(file)
-      url = hd(data["url"])["href"]
 
       assert {:ok, actor} =
                Actors.update_actor(
                  actor,
-                 Map.put(@update_attrs, :avatar, %{name: file.filename, url: url})
+                 Map.put(@update_attrs, :avatar, %{name: file.filename, url: data.url})
                )
 
       assert %Actor{} = actor