Bring back :send_user_agent for test env only.

Too many tests break as they don't include injected user agent in expected response

config/test.exs

@@ -96,6 +96,8 @@ config :pleroma, :rate_limit, %{}
 
 config :pleroma, :http_security, report_uri: "https://endpoint.com"
 
+config :pleroma, :http, send_user_agent: false
+
 rum_enabled = System.get_env("RUM_ENABLED") == "true"
 config :pleroma, :database, rum_enabled: rum_enabled
 IO.puts("RUM enabled: #{rum_enabled}")

lib/pleroma/http/request_builder.ex

@@ -10,6 +10,8 @@ defmodule Pleroma.HTTP.RequestBuilder do
   alias Pleroma.HTTP.Request
   alias Tesla.Multipart
 
+  @mix_env Mix.env()
+
   @doc """
   Creates new request
   """
@@ -33,13 +35,7 @@ defmodule Pleroma.HTTP.RequestBuilder do
   """
   @spec headers(Request.t(), Request.headers()) :: Request.t()
   def headers(request, headers) do
-    headers_list =
-      with nil <- Enum.find(headers, fn {key, _val} -> String.downcase(key) == "user-agent" end) do
-        [{"user-agent", Pleroma.Application.user_agent()} | headers]
-      else
-        _ ->
-          headers
-      end
+    headers_list = maybe_add_user_agent(headers, @mix_env)
 
     %{request | headers: headers_list}
   end
@@ -91,4 +87,16 @@ defmodule Pleroma.HTTP.RequestBuilder do
     |> Map.from_struct()
     |> Enum.into([])
   end
+
+  defp maybe_add_user_agent(headers, :test) do
+    with true <- Pleroma.Config.get([:http, :send_user_agent]) do
+      [{"user-agent", Pleroma.Application.user_agent()} | headers]
+    else
+      _ ->
+        headers
+    end
+  end
+
+  defp maybe_add_user_agent(headers, _),
+    do: [{"user-agent", Pleroma.Application.user_agent()} | headers]
 end

test/pleroma/reverse_proxy_test.exs

@@ -27,6 +27,7 @@ defmodule Pleroma.ReverseProxyTest do
     end
 
     test "use Pleroma's user agent in the request; don't pass the client's", %{conn: conn} do
+      clear_config([:http, :send_user_agent], true)
       # Mock will fail if the client's user agent isn't filtered
       wanted_headers = [{"user-agent", Pleroma.Application.user_agent()}]
 
@@ -164,10 +165,7 @@ defmodule Pleroma.ReverseProxyTest do
 
     test "header is filtered", %{conn: conn} do
       # Mock will fail if the accept-language header isn't filtered
-      wanted_headers = [
-        {"user-agent", Pleroma.Application.user_agent()},
-        {"accept-encoding", "*"}
-      ]
+      wanted_headers = [{"accept-encoding", "*"}]
 
       Tesla.Mock.mock(fn %{url: "/headers", headers: ^wanted_headers} ->
         %Tesla.Env{