store meta data about requests in a data store

[guenterh]

it would be reasonable to include a data store for meta data about the requests and the processing result

• id of sent record
• timestamp
• action type of the message (create / replace / delete)

This would give us the possibility for better monitoring of the requests sent to the Search engine platform and to compare the results of the Search engine with the messages sent to the platform

• probably we could use Mongo as data store
• there should be a configuratuion to activate / deactivate the datastore