config: make sending the user agent configurable, disable sending the user agent in tests

config/config.exs

@@ -192,6 +192,7 @@ config :tesla, adapter: Tesla.Adapter.Hackney
 # Configures http settings, upstream proxy etc.
 config :pleroma, :http,
   proxy_url: nil,
+  send_user_agent: true,
   adapter: [
     ssl_options: [
       # We don't support TLS v1.3 yet

config/test.exs

@@ -63,6 +63,8 @@ config :pleroma, :app_account_creation, max_requests: 5
 
 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}")