[ui_actions] Remove declare module pattern for trigger/action mappings

[lukeelmers]

Currently the ui_actions plugin exposes TriggerContextMapping and ActionContextMapping as interfaces that can be augmented by other plugins which are registering custom triggers/actions like so (example from data):

declare module '../../ui_actions/public' {
  export interface TriggerContextMapping {
    [APPLY_FILTER_TRIGGER]: ApplyGlobalFilterActionContext;
  }

  export interface ActionContextMapping {
    [ACTION_GLOBAL_APPLY_FILTER]: ApplyGlobalFilterActionContext;
    [ACTION_SELECT_RANGE]: SelectRangeActionContext;
    [ACTION_VALUE_CLICK]: ValueClickActionContext;
  }
}

This pattern was originally borrowed from core's RouteHandlerContext, however this is something we are looking to move away from.

While the simplicity of importing a single interface for everything in a registry is convenient, it can create implicit dependencies between plugins. (If your plugin depends on a trigger registered by another plugin, you should import any necessary types directly from that plugin instead of accessing it indirectly via the ui_actions typings).

One strategy for solving this could be removing the "mapping" interfaces and instead modifying generic type params where applicable, so that folks can specify the expected return types which you cast to internally, e.g.

uiActions.getTrigger<ValueClickActionContext>(ACTION_VALUE_CLICK);

Alternatively you can put the responsibility on consumers to directly do casting:

uiActions.getTrigger(ACTION_VALUE_CLICK) as ValueClickActionContext;

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[vadimkibana]

Closing as this was completed some time ago.