Add Twitter Filter request parameter for language

[kerchner]

As per the Twitter documentation, there are other request parameters available for Filter and Search streaming API methods:

• https://developer.twitter.com/en/docs/tweets/filter-realtime/api-reference/post-statuses-filter.html
  See language and filter_level which are available at any API access level.

• https://developer.twitter.com/en/docs/tweets/filter-realtime/api-reference/post-statuses-filter.html
  See lang, locale, geocode, result_type

The use case here is a researcher who wishes to collect Tweets only in a certain langauge.

[kerchner]

A second researcher I just met with also would benefit from being able to add --language to a twitter filter stream.

[kerchner]

Updates:

The first link (in the initial comment) no longer contains any references to language or filter_level. However, this content seems to still exist, instead at:
https://developer.twitter.com/en/docs/tweets/filter-realtime/guides/basic-stream-parameters

I believe the second link (in the initial comment) was meant to refer to the Search API:
https://developer.twitter.com/en/docs/tweets/search/api-reference/get-search-tweets.html

[kerchner]

It appears that implementing this feature for Twitter Filter collections will require enhancing Twarc.filter - note that https://github.com/DocNow/twarc/blob/1.6.1/twarc/client.py#L296 currently does not yet feature use of the language parameter.

Twarc.search does appear to currently provide a lang parameter - see https://github.com/DocNow/twarc/blob/v1.6.1/twarc/client.py#L72

In terms of milestone 2.1, perhaps the goal should be to fork Twarc, submit a PR to Twarc and write the SFM code to exercise it. If Twarc merges the PR before we are ready to tag 2.1, then we can use it. Otherwise, we can keep in a branch for the next release (rather than using a fork of Twarc).

[kerchner]

Spun #966 off to enhance Twitter search. This ticket will now be focused on Twitter filter, and will depend on making changes to Twarc.filter().

[kerchner]

Note enhancement in Twarc: https://github.com/DocNow/twarc/releases/tag/v1.7.1