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

lib/mobilizon_web/schema/comment.ex

@@ -35,7 +35,7 @@ defmodule MobilizonWeb.Schema.CommentType do
     @desc "Create a comment"
     field :create_comment, type: :comment do
       arg(:text, non_null(:string))
-      arg(:actor_username, non_null(:string))
+      arg(:actor_id, non_null(:id))
 
       resolve(&Comment.create_comment/3)
     end

lib/mobilizon_web/schema/event.ex

@@ -63,7 +63,7 @@ defmodule MobilizonWeb.Schema.EventType do
 
     field(:draft, :boolean, description: "Whether or not the event is a draft")
 
-    field(:participant_stats, :participant_stats, resolve: &Event.stats_participants_for_event/3)
+    field(:participant_stats, :participant_stats)
 
     field(:participants, list_of(:participant), description: "The event's participants") do
       arg(:page, :integer, default_value: 1)
@@ -112,13 +112,21 @@ defmodule MobilizonWeb.Schema.EventType do
   end
 
   object :participant_stats do
-    field(:approved, :integer, description: "The number of approved participants")
-    field(:unapproved, :integer, description: "The number of unapproved participants")
+    field(:going, :integer,
+      description: "The number of approved participants",
+      resolve: &Event.stats_participants_going/3
+    )
+
+    field(:not_approved, :integer, description: "The number of not approved participants")
     field(:rejected, :integer, description: "The number of rejected participants")
 
-    field(:participants, :integer,
+    field(:participant, :integer,
       description: "The number of simple participants (excluding creators)"
     )
+
+    field(:moderator, :integer, description: "The number of moderators")
+    field(:administrator, :integer, description: "The number of administrators")
+    field(:creator, :integer, description: "The number of creators")
   end
 
   object :event_offer do