FIX QuerySort::sort method should support sorting for multi arguments

[sabina-talipova]

Description

Even if a method receives several parameters, then sorting occurs by the field of the arguments that is last specified in the schema, and not in the passed parameters. That is, if SilverStripe\GraphQL\Tests\Fake\DataObjectFake has the following schema

fields:
    myField: true
    AuthorID: true

and sorting is required AuthorID => DESC, myField => ASC, then sorting was done only by AuthorID, since in the schema this field is indicated after myField.
Therefore, the call $list->sort() must be completed after all the necessary processing has been carried out.

Parent issue

• MariaDB - failing integration test #561

[GuySartorelli]

This can't be MNT since it's changing actual code that projects will be using.

If the changes in the QuerySort class are fixing a bug, you should use FIX and the commit message should explain what the bug is that's being fixed.
If they're just an enhancement, then use ENH and the commit message should explain what the enhancement is.

[GuySartorelli]

The reason changing the order of the fields in the schema affected the results is because the underlying GraphQL library we're using ignores the order that fields are entered in the query arguments. It uses the order that the fields were defined in the schema.

I've added a new commit on top of yours to resolve this. It also changes the test to use a query provider so it will run all of the FilterAndSort scenarios even if one fails. I removed the scenarios that had commented out tests because they weren't actually contributing anything to the test coverage.

Normally I would have asked you to make those changes, but I didn't know what changes were necessary or even possible - and to find that out I had to essentially do the full implementation. At that point it was just easier to commit that implementation rather than ask you to redo what I had just done.

Next steps

1. Have a look over this code and test it locally to make sure you're happy with it. This is still your PR, so make any changes you think are appropriate.
2. Add another test scenario where we sort first by myField and then by AuthorID to protect us against regressions
3. Add new test coverage to check this works correctly with a normal read (not read one - but read many) query
4. See if changes similar to what I've made are necessary in src/Schema/Plugin/SortPlugin.php

[GuySartorelli]

Please also check if this bug affects graphql 4 - if so, we need to retarget to 4.3

[sabina-talipova]

Open new PR for 4.3:

• FIX QuerySort::sort method should support sorting for multi arguments #563