Add keywords search (label, description, aggregator name) for Usage Data Providers

Add keywords search (label, description, aggregator name) for Usage Data Providers.

The front end can use this CQL query to execute a full text search on all three fields:

keywords all “foo bar baz”

A similar keywords search has been implemented in the users app.

Combining multiple single-field searches using OR may result in slow full table scans because the PostgreSQL query planner cannot estimate across the ORs.

Use case: UB Greifswald want to maintain and search for the product name put into the description field.