Add save points to fix it

Unsure if this is right approach but it does work. Oddly only postgres was complaining about the poisoned transaction.

lib/flipper/adapters/active_record.rb

@@ -1,4 +1,5 @@
 require 'set'
+require 'securerandom'
 require 'flipper'
 require 'active_record'
 
@@ -244,17 +245,26 @@ def delete(feature, gate)
       end
 
       def enable_multi(feature, gate, thing)
-        with_connection(@gate_class) do
-          @gate_class.create! do |g|
-            g.feature_key = feature.key
-            g.key = gate.key
-            g.value = thing.value.to_s
+        with_connection(@gate_class) do |connection|
+          begin
+            connection.transaction do
+              savepoint_name = "flipper_savepoint_#{SecureRandom.hex(8)}"
+              connection.execute("SAVEPOINT #{savepoint_name}")
+              begin
+                @gate_class.create! do |g|
+                  g.feature_key = feature.key
+                  g.key = gate.key
+                  g.value = thing.value.to_s
+                end
+              rescue ::ActiveRecord::RecordNotUnique
+                # already added so no need move on with life
+                connection.execute("ROLLBACK TO SAVEPOINT #{savepoint_name}")
+              end
+            end
           end
         end
 
         nil
-      rescue ::ActiveRecord::RecordNotUnique
-        # already added so no need move on with life
       end
 
       def result_for_gates(feature, gates)