Enhance Widget Export API

[DRay]

Add the ability to programmatically export a Widget with specific filters and/or to export it as a certain user using the /dashboard/{id}/widgets{id}/ endpoint.

User Story#1

As an admin I want to make api calls to the widget pdf export endpoint and include userid and custom filters so that I can download an export on behalf of another user in the system and specify the filters 

Acceptance Criteria

I can pass 2 properties to the export endpoint: User Id and filters

Both parameters are optional and can be used separately from each other

If a user Id parameter is provided, the Widget is exported on behalf of the provided user including the current filters applied and data security rules.

If a custom filters parameter is provided, the Widget is exported with the custom filters. There is no merge between the existing Widget filters and the custom filters parameter. 

The is an option to provide an empty custom filters parameter, in this case, no filters are applied to the dashboard. 

User story #2

As a user (not admin) I want to make api calls to the Widget pdf export endpoint and include custom filters so that I can download an export with custom filters 

Acceptance Criteria

I can pass a custom filters parameter to the export to the Export endpoint

The custom filters parameter is a jaql query that will replace the current dashboard filters

The custom filters will respect my data security 

I can provide an empty custom filters parameter that will remove all filters from the report.