Ensure sort order is set on option text field for attributes using so…

[romainruaud]

…urce.

This is a fix for #450

See my comment explaining the problem : #450 (comment)

Imho, this fix is sufficient for 2.3.x branch.

But we should consider refactoring a bit the way we handle field name mapping in the collection for the next 2.4.x release. What I have in mind would be a FieldNameMapperInterface or something like this, which could handle these operations, and we could inject into the collection but also everywhere else we need to access the mapping (virtual categories, search API, and so on...) instead of duplicating a dirty "mapFieldName" function everywhere.

Let me know,

[romainruaud]

@afoucret any new about this one ?

[romainruaud]

PR Updated :

• inject proper field name for attributes directly via addSortFilterParameter

• little change to prepareSortOrder function :

previously, the $sortField was erased because it was recomputed from $attribute even if found in _productLimitationFilters.

This was leading to the following issue : first "option_text_manufacturer" was properly pulled from _productLimitationFilters, but then overwritten by mapFieldName($attribute) where $attribute is the "real" attribute code without the "option_text_" prefix