Overhaul actions

[radiac]

The current mechanism for defining actions (urls and links) is messy.

They're currently built by the vg based on which views are defined. This is inflexible; views should support multiple actions, different types of actions etc, and we're missing a way to add djagno admin-style lists actions.

Plan:

• Remove from there and put on the views themselves as .actions
• View.get_actions() should check for .actions otherwise build its own from .viewgroup
• They're used to define which actions appear on the page.
• List of Action classes, eg [IndexAction, CreateAction]
• Action class can specify styling/icons and a URL (index, create). Appears at top.
• ActionObject as Action, URL points at an object (update, delete). In item "sidebar"
• ActionQuerySet class as Action, but URL takes multiple objects (delete). At top as dropdown.
• ActionField as ActionObject but also takes a field
  • target for this feature: an inline approve toggler, eg a boolean. Would need some templates/text strings to give context, and some JS/htmx
• Also accept a list of view names, eg ["index", "create"] which are turned into an Action
• View.action - default action class for when used as a string.
• Actions should have a way to declare a JS/API version; render()? examples:
  • approve/unapprove go ticking down a list etc
  • update inline
  • delete without leaving page
• subclass ActionQuerySet to manage the dropdown action
• and ActionField to hook into javascript for an Approve button
• But does this complicate things unnecessarily?
  • View.as_action() could check .action and fall back to wrap Action/ActionObject by default, then View.get_actions() can have a list like ["change", "delete", ApproveAction] etc