Move part of catalog.newcontext.products classes to QuerySet

[duker33]

This set of classes are not contexts. They don't have their own context data, but have only QuerySet logic.
Later we discussed this module using at site with the architect. And Artemiy said, that this classes are semantically separated from others in this module
fidals/shopelectro#689 (comment)

If we'll move it's logic to QuerySets, we'll make this semantic more clear.

ActiveProducts
OrderedProducts
PaginatedProducts
ProductsByCategory
TaggedProducts

[duker33]

@artemiy312 , what do you think about this proposal?

[ArtemijRodionov]

Yes, we can do it. It looks like the django-way approach.
Unfortunately it will lead to giant and imperative QuerySet classes, but it seems unavoidable when working with ORM and django

Also we can remove some tags context classes in favor of QuerySet methods.
PaginatedProducts we should leave, because it isn't working only with QuerySet.

As the result only PaginatedProducts, ProductImages, ProductBrands, GroupedTags will remain.

[duker33]

@artemiy312 , we can organise this code in a right way. It'll take not more space, then it taken in contexts now.

PaginatedProducts does this two things:

• just forwards refarm_pagination.context.PaginationContext class for context data.
• uses the class for queryset processing refarm_pagination.context.PaginationContext

Despite this two operations uses the same class, they are separated semantically. So, we can split them: the first peace we just throw away. The second one goes to queryset.

So, i'll propose some code

[duker33]

i'll adapt SE to the new refarm's code in the same task

[0pdd]

@duker33 the puzzle #266 is still not solved.

[0pdd]

@duker33 the puzzle #308 is still not solved; solved: #266.