Reorganize My Assignments page

Currently, a user’s My Assignments page lists all undefaulted assignments from oldest to newest, and then all undefaulted pinch hits from oldest to newest. All are listed on a single page, without pagination.

To make it easier to find the most pressing information – your newest assignments, waiting to be filled – we would like to make some changes:

• Split assignments across two pages like we do with the My Claims page: the default URL (https://test.archiveofourown.org/users/testy/assignments) should list unposted assignments, and https://test.archiveofourown.org/users/testy/assignments?posted=true should list complete assignments.

• Navigation links for “Unposted Assignments” and “Completed Assignments” should be added after the page heading. They should use span_if_current to indicate which you are accessing. (These are the terms in the Status info of the blurbs on the page, more or less – they use “Complete!” rather than “Completed”.)

• Each page should list all appropriate assignments from newest to oldest regardless of whether they're pinch hits or not.

• When necessary, pages should be paginated at top and bottom, using the default number of items for pagination.

• The "Assignments (#)" count in dashboard sidebar to only include unposted assignments, like "Claims (#)" only includes unfulfilled.

• The note about checking for claims prompts should have the class notes instead of note – bonus points if you change the Claims page as well. (And maybe add a period to the “Try X” sentences.)