DB Search visualization: Authentication context

[mrsimpson]

Problem description

When triggering an implicit search, the Solr-based Search provider may need to set-up authentication prior to executing the search. This is the case for DB search: Only after an explicit login is triggered, the authenticated results are being returned. Else, the Smarti widget can only display anonymously available results.

Proposal

Add a configuration to the search provider which allows to define hooks-methods.
Possible, initialization, preQueryExecution and PostQueryExecution are useful events.
The Smarti-widget shall interpret this configuration and trigger the callbacks.