add "Edit week planner"-function

[gcode-de]

add functions to

• (re)assign random recipes to weekdays
• remove assigned recipe from weekday
• set number of servings for weekday and respect them when visiting details page of a recipe from the planner
• set randomness of "auto assign" function for the whole week (function will follow soon!)

Note: UI updates are relatively slow as DB access is required for most of them. We will be considering using optimistic updates in the future.