Get rid of Pleroma.Config in favor of Application

Discussed in https://git.pleroma.social/pleroma/pleroma/merge_requests/426#note_7232

lib/pleroma/application.ex

@@ -10,7 +10,6 @@ defmodule Pleroma.Application do
     # Define workers and child supervisors to be supervised
     children =
       [
-        worker(Pleroma.Config, [Application.get_all_env(:pleroma)]),
         # Start the Ecto repository
         supervisor(Pleroma.Repo, []),
         worker(Pleroma.Emoji, []),

lib/pleroma/config.ex

@@ -1,15 +0,0 @@
-defmodule Pleroma.Config do
-  use Agent
-
-  def start_link(initial) do
-    Agent.start_link(fn -> initial end, name: __MODULE__)
-  end
-
-  def get(path) do
-    Agent.get(__MODULE__, Kernel, :get_in, [path])
-  end
-
-  def put(path, value) do
-    Agent.update(__MODULE__, Kernel, :put_in, [path, value])
-  end
-end

lib/pleroma/web/activity_pub/activity_pub_controller.ex

@@ -6,7 +6,6 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubController do
   alias Pleroma.Web.ActivityPub.Relay
   alias Pleroma.Web.ActivityPub.Utils
   alias Pleroma.Web.Federator
-  alias Pleroma.Config
 
   require Logger
 
@@ -15,7 +14,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubController do
   plug(:relay_active? when action in [:relay])
 
   def relay_active?(conn, _) do
-    if Config.get([:instance, :allow_relay]) do
+    if Keyword.get(Application.get_env(:pleroma, :instance), :allow_relay) do
       conn
     else
       conn

lib/pleroma/web/federator/federator.ex

@@ -7,7 +7,6 @@ defmodule Pleroma.Web.Federator do
   alias Pleroma.Web.ActivityPub.Relay
   alias Pleroma.Web.ActivityPub.Transmogrifier
   alias Pleroma.Web.ActivityPub.Utils
-  alias Pleroma.Config
   require Logger
 
   @websub Application.get_env(:pleroma, :websub)
@@ -72,7 +71,7 @@ defmodule Pleroma.Web.Federator do
         Logger.info(fn -> "Sending #{activity.data["id"]} out via Salmon" end)
         Pleroma.Web.Salmon.publish(actor, activity)
 
-        if Config.get([:instance, :allow_relay]) do
+        if Keyword.get(Application.get_env(:pleroma, :instance), :allow_relay) do
           Logger.info(fn -> "Relaying #{activity.data["id"]} out" end)
           Relay.publish(activity)
         end