feat: allow to filter events by local-only

In addition to internal (self + federated) and global (global external search engine), introduce the
self possibility

Closes #1322

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/graphql/schema/search.ex

@@ -160,6 +160,8 @@ defmodule Mobilizon.GraphQL.Schema.SearchType do
   end
 
   enum :search_target do
+    value(:self, description: "Search only on content from this instance")
+
     value(:internal,
       description: "Search on content from this instance and from the followed instances"
     )