After talking to the search team we're going to store the qualifiers in the search index in statement_keywords. Each statement will be stored without qualifiers, and then separately with each qualifier

For example, on wikidata the Mona Lisa has the statement 'depicts woman' P180=Q467 and the statement 'depicts sky' P180=Q527 with the qualifiers 'applies to part background' P518=Q13217555 and 'color green' P462=Q3133.

We propose to store these in statement_keywords as follows:

'statement_keywords' : [
    'P180=Q467',
    'P180=Q527',
    'P180=Q527[P518=Q13217555]',
    'P180=Q527[P462=Q3133]',
]

In this way the user will be able to search using the haswbstatement keyword. If they want to find items with 'depicts sky' then can search for haswbstatement:P180=Q527, where if they want to find items that depict a green sky they can search for haswbstatement:P180=Q527[P462=Q3133]