Return item notes with search results

In order to not make the response very large, a admin can define a
limit on how much to return.

modules/restserver/src/main/resources/reference.conf

@@ -24,6 +24,12 @@ docspell.server {
   # depending on the available resources.
   max-item-page-size = 200
 
+  # The number of characters to return for each item notes when
+  # searching. Item notes may be very long, when returning them with
+  # all the results from a search, they add quite some data to return.
+  # In order to keep this low, a limit can be defined here.
+  max-note-length = 180
+
   # Authentication.
   auth {