only create checksums for non-existing checksums

This commit fixes an issue that results in error message spam on
the PostgreSQL server. We were previously attempting an insert on
the checksums table for all checksums that belong to a cookbook, even
if they already existed in the database. Because we were rescuing the
conflict, we weren't actually seeing errors, just log spam from
PostgreSQL. This commit ensures that we don't send inserts for
checksums that we already know exist.
Merge branch 'sd/skip-existing-checksums'
Add organization_authz_id base state record field

Fetch the authz information at the same time we fetch the org guid,
and stuff it into the base state record. This simplifies bits of the
organizations and association endpoints.
Use correct routine to fetch authz_id as well as org guid.
fetch_org_guid_and_authz -> fetch_org_metadata
DEV: chef_db from ma/fetch_org_authz
Merge branch 'ma/fetch_org_authz'
helpers for associations and organization
add support for optional resource_arg to resource initializers and base state
add invitation support to utility functions
add organization_authz_id base state record field
correct error messages for passing tests