Show search source badges only with show_sources param

The badges are a debugging aid - render them only when explicitly
requested via ?show_sources=1 instead of on every search.

app/helpers/packages_helper.rb

@@ -1,4 +1,10 @@
 module PackagesHelper
+  # Search result origin badges are only shown when explicitly
+  # requested via ?show_sources=1
+  def search_sources_visible?
+    params[:show_sources].present?
+  end
+
   # Human readable label for the search strategy that put a package
   # into the search results (see PackagesController#search_packages)
   def search_source_label(source)