support congress as a top level searchable element in the API

[relarson1]

For many of the collections they are congress specific and in the package info they have the congress in them
for example the bills collection:
package level has:"congress": "115",
but at the collection level that information is not available:
https://api.govinfo.gov/collections/BILLS/2018-01-01T00:00:00Z?offset=0&pageSize=10&api_key=

"packageId": "BILLS-115hr609enr",
"lastModified": "2018-11-01T14:59:34Z",
"packageLink": "https://api.govinfo.gov/packages/BILLS-115hr609enr/summary",
"docClass": "hr",
"title": "An Act T

It would be very helpful for downloading to allow searching and filtering by congress at the collection level, similar to how docClass was added for the CDOC collection
i.e.
https://api.govinfo.gov/collections/BILLS/2018-01-01T00:00:00Z?offset=0&pageSize=10&congress=115&api_key=
and return only 115th items for that time period.

[jonquandt]

This is now available. Note that for the following collections, we are performing some reindexing to get the congress values to appear at the package level:

CREC
ECONI
HJOURNAL
HMAN
HOB
SMAN
STATUTE

This republishing will take some time (several weeks), and we will be focusing on the most recent documents. New day-forward content in these collections will have the Congress values as soon as they are added to the system.