Provide admin endpoint section in the config by docker setup

docker/docker-compose/docspell.conf

@@ -34,6 +34,17 @@ docspell.server {
       header-value = ${?DOCSPELL_HEADER_VALUE}
     }
   }
+
+  # This is a special endpoint that allows some basic administration.
+  #
+  # This is used for some endpoints, for example:
+  # - re-create complete fulltext index:
+  #   curl -XPOST -H'Docspell-Admin-Secret: xyz' http://localhost:7880/api/v1/admin/fts/reIndexAll
+  admin-endpoint {
+    # The secret. If empty, the endpoint is disabled.
+    secret = ""
+  }
+
   # Configuration of the full-text search engine.
   full-text-search {
     enabled = true