paginated inbox

[catdevnull]

fixes hyphacoop/distributed-press-organizing#163

• add some way to automatically add indexes to existing inboxes

[RangerMauve]

Great start, mind also adding a test to make sure that stuff is sorted?

• create fake posts
• have their id be incrementing (a,b,c) but their publish time decrementing (3,2,1)
• do a list and check that the order is correct
• also test with limit=1 and skipping.

[RangerMauve]

Great! Lets just get some small tests in to make sure it's working and then it looks good to me. :)