fix(http): make Hackney use HTTP/1.1 only

Hackney 4 negotiates HTTP/2 and shares one connection per host. The
media proxy closes a response with :hackney.close/1, which stops the
whole connection, so parallel downloads from one host broke each other.

changelog.d/hackney-http1.fix

@@ -0,0 +1 @@
+Hackney: use HTTP/1.1 only, so closing one media proxy response no longer breaks other downloads from the same host

config/config.exs

@@ -163,6 +163,10 @@ config :mime, :types, %{
 
 config :tesla, adapter: Tesla.Adapter.Hackney
 
+# Hackney 4 shares one HTTP/2 connection per host, and closing one response
+# (as the media proxy does) stops it for every other stream on it.
+config :hackney, default_protocols: [:http1]
+
 # Configures http settings, upstream proxy etc.
 config :pleroma, :http,
   proxy_url: nil,

test/pleroma/http/adapter_helper/hackney_test.exs

@@ -13,6 +13,12 @@ defmodule Pleroma.HTTP.AdapterHelper.HackneyTest do
     {:ok, uri: uri}
   end
 
+  # Hackney 4 shares one HTTP/2 connection per host, and closing a response
+  # stops that connection for every stream on it.
+  test "Hackney only speaks HTTP/1.1" do
+    assert :hackney_util.default_protocols() == [:http1]
+  end
+
   describe "options/2" do
     setup do: clear_config([:http, :adapter], a: 1, b: 2)