feat: add pagination to the HomePageCoursesV2 API

[mariajgrimaldi]

Description

This PR builds pagination capabilities on top of the new HomePageCourses API version. These changes are intended to be used by the new Course Home MFE. The new API is based on HomePageCourses with tweaks, so it gets courses with Course Overview helpers that allow filtering, ordering, and pagination with Django/DRF methods and classes.

API changes compared to V1

Besides the changes mentioned here that add filtering/ordering capabilities, we:

1. Used a simple paginator object before returning the courses list; this paginator only considers the list of CourseOverviews returned by the contentstore utilities.
2. Since iterators don't have length, they can't be paginated. So we had to convert the filter(course_filter, courses_summary) iterator into a list to paginate later.
3. We added a setting configuration for the API page size.

Supporting information

For more information on this enhancement, please check:
https://openedx.atlassian.net/wiki/spaces/OEPM/pages/4032856101/Studio+Home+incremental+upgrades+-+product+approach

Testing instructions

Login as an administrator or as course staff (they should both work), then:
You can use your browser to get your list of courses from Studio HTTP(s)://<CMS_HOST>/api/contentstore/v2/home/courses where the list of courses will appear paginated:

Deadline

This effort is part of the Spanish consortium project, so it'd be ideal to merge this before the end of the project.

Other information

There are still some architectural decisions to be made around how to present data to the Studio Home MFE, ie. how to split active/archived courses. So, we'll be updating this PR accordingly.

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[mariajgrimaldi]

Note to reviewer: I'm a bit worried about the performance impact of this change, but this was one of the alternatives which included fewer changes to the current source code.

[mariajgrimaldi]

Note to reviewer: I'm unsure how to handle this case. In this view, not only courses are returned, but also returns in_process_course_actions which is a list of CourseRerunState objects not necessarily related to the courses list so I'm not sure why they're currently returned together.

So I didn't add pagination to in_process_course_actions since I believe that that list should be returned by another different view dedicated only to course reruns state objects.

What do you think? That new view is out of the scope of this PR, so this new view returns the list of course reruns objects without pagination.

[BryanttV]

I don't think we currently need this paginated list, I don't see a problem to leave it like that for the moment, and work on it later in a dedicated PR if necessary.

[johnvente]

Hi there @mariajgrimaldi! Could you please add num_pages that will indicate the number of pages available? This means, for instance, if I had 20 courses and the items per page is 10, then the num_pages would be 2

[johnvente]

Hi there @mariajgrimaldi! This is working as expected. My only concern is about setting the number of items peer page but is not a blocking is a nice to have. LGTM

[mariajgrimaldi]

Note to reviewer
I'm currently studying which parts of the implementation are affecting performance. Based on those results, this or the count might have to go.

[mariajgrimaldi]

I'll merge this PR to the V2 API implementation.

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