Release 2118
Trello card
Context
We recently moved the old expired placement requests for fixed dates to the archived page, so to help declutter the manage requests page for schools that have many old requests that don't want to process.
Schools with flex dates now have the same problem, so we want to move requests for flex dates that are unprocessed for longer than two months in the archived page as well.
Changes proposed in this pull request
Expand the model scopes to include flex dates too and also mark them as expired in the UI.