* Add some more checks to remove PHP warnings / notices.
* Adjust code to match CMS 9 API / interfaces.
* Do no longer use "query" but only searchTerm, as query is internal
API.
Instead of hardcoding and tight coupling of relation resolving, we now
provide a dataprocessor instead.
Therefore you need to configure resolving for each indexed type.
This resolves#149 and #147.
Use own service to handle data processing. Classes like indexer should
not know anything about the structure and how to process the data.
Also rename record to data, as we can process just any data in form of
an array.
Relates: #116
Add a new processor, with docs and tests, to allow removal of fields
before sending them to search service like elasticsearch.
E.g. remove sensitive information that should not be available.