split keywords by , in facet, then recalculate

[pvgenuchten]

Overview

This PR introduces a procedure which splits keywords by ',' and recalculates totals after db query
Similar mechanism could be used for other fields which are ,-separated
I see 2 alternatives for this PR:

• keywords not to be stored as concatenated string, but actual list
• introduce an in-db procedure to split the keywords-string as part of the facet query

Related Issue / Discussion

resolves #1065

Additional Information

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