Add conditional for hiding bills with restricted views

[reginafcompton]

This PR adds a conditional to the is_visible property: it explicitly hides bills marked as having a restricted view in Legistar.

It works in cooperation with opencivicdata/scrapers-us-municipal#258, opencivicdata/python-legistar-scraper#81, and datamade/django-councilmatic#232

N.b., I'll get the tests passing once I can add the above-mentioned changes in Django Councilmatic to the testing requirements.

[reginafcompton]

Overview

With the newly provided API token, DataMade scrapers now have access to private Metro bills. But….why do we need to scrape private bills?

We need to know which bills to show and which bills to hide on Councilmatic: the MatterRestrictedViewViaWeb field tells us which bills are public (show!) and which are private (hide!). The process:

1. scrape bill and include the value of MatterRestrictedViewViaWeb in the extras (Add token to params opencivicdata/scrapers-us-municipal#258 and Scrape private opencivicdata/python-legistar-scraper#81)
2. import bills and indicate if they are restricted (Add field to mark bills with a restricted view, and import it datamade/django-councilmatic#232)
3. hide or show bills based on this value. (this PR)

But wait. Why not just skip private bills? Sometimes, Metro will toggle bills between public and private, meaning that the Councilmatic system may have bills that were previously public. Scraper needs to access those now-private bills, so that Councilmatic can make sense of their new status.

Not knowing which bills had changed between public and private has caused issues in the past:
#345 (comment)
#328

---

N.b. We do know that toggling “Not viewable in site” changes the timestamp of bills: https://docs.google.com/document/d/1Huv0kRQmRm-I658JE4hG8rQSdmtjy-8QUSr_cwWZnHI/edit#heading=h.hrplgr8t7ccr

Hence, the scraper should catch when a bill changes between public to private.

[hancush]

a+

[hancush]

:)