Adding boost number for each fields for edismax query

[kylehuynh205]

What does this Pull Request do?

For edismax solr query (https://github.com/Islandora/advanced_search/blob/2.x/src/AdvancedSearchQuery.php#L255-L256) when Advanced Search's request triggered, the list of fields which is passed to qf= (more on this at https://solr.apache.org/guide/solr/latest/query-guide/edismax-query-parser.html)

score random boost_document ss_author ds_changed ds_created itm_edtf_year .....

However there is no boost number which can be configured in Search API Solr index https://sandbox.islandora.ca/admin/config/search/search-api/index/default_solr_index/fields

This PR is add the code to attach the boost number for each field, for example:

ss_author^1 ds_changed^1 ds_created^1 itm_edtf_year^1 sm_field_award_received^1 tm_X3b_en_field_description^8

What's new?

https://github.com/digitalutsc/advanced_search/blob/kylehuynh205-patch-1/src/AdvancedSearchQuery.php#L255-L271

[rosiel]

Looks good to me, and it works (my dismax queries re-ordered themselves and boost-worthy content was boosted.)