Fix compat with ruby < 2.5

lib/pg_ldap_sync.rb

@@ -1,4 +1,5 @@
 require "pg_ldap_sync/application"
+require "pg_ldap_sync/compat"
 require "pg_ldap_sync/version"
 
 module PgLdapSync

lib/pg_ldap_sync/compat.rb

@@ -0,0 +1,9 @@
+#!/usr/bin/env ruby
+
+class Hash
+  def transform_keys
+    map do |k, v|
+      [yield(k), v]
+    end.to_h
+  end unless method_defined? :transform_keys
+end