proposal: passing filters to registries through $state.params

[jniles]

We have begun to experiment with filters that are applied to a registry through $state parameters. For example, the Cash Registry implements them by:

1. Adding filters and display to the route.
2. Assigning the values to Cash.filters at startup.

This was a good first implementation, but has a number of drawbacks:

1. The API of filters and display isn't obvious what goes where. It turns out, display is never used. I believe this was a hold-over from the old way of specifying filters.
2. It isn't clear which filters take precedence - the cached ones or the $state ones? Can the $state ones replace default filters?
3. Only one filter can ever be used at a time from $state (in the current implementation).

Design

Building off the current implementation, I propose we adopt a new way of passing filters from $state. Every registry that accepts external filters will provide a top-level filters array in the parameters, defined in this way:

$stateProvider.state('someState', {
  url : '/xyz',
  controller : 'SomeCtrl',
  templateUrl :'some-template.html',
  params : { filters : [ ] }
});

In the startup method, we can simply check if the filters exist like this:

var hasStateFilters = $state.params.filters.length > 0;

If they do, we load them into the current view:

if (hasStateFilters) {
  ControllerService.filters.replaceFiltersFromState($state.params.filters);
  ControllerService.cacheFilters();
}

The only difference between replaceFilters and replaceFiltersFromState is an extra angular.copy().

A filter would be defined in the usual way:

filters = [
  { key : 'account_id', value :1234 },
  { key : 'patient_uuid', value : 'some-long-uuid' }
];

Other Thoughts

1. We could optionally specify if the filters should be merged, overwritten, or temporary (not cached). I'm not sure what the best implementation should be.

[jniles]

This was also implemented and got approval in #2018.

[jniles]

This is already largely in use, but I'll keep this open for reference.