Save filter with issue board
Description
Being able to create a new issue board is awesome, but sometimes you need to save a filter along with the issue board to make sense. e.g. The CI team uses an issue board with defined columns but also filters the entire board by the ~CI label. We should be able to somehow store that filter with the board definition.
Note, I'm torn on whether milestones should be stored with the board or not. Do you really want to make new boards for each milestone, or just have one board definition? Then again, I guess that's what filtering by "Upcoming" is for.