feat: support newer versions of django (4.2)

Closes #19

See merge request !21

remove vendored ibisclient

Closes #16

See merge request !20

Remove the vendored ibisclient, preferring to use the upstream PyPI one.

Python 2 has been EoL-ed and we no longer support it.

Add the supported LTS Django versions. As of writing Django 3.1 is
EoL-ed in a week so it doesn't seem worth keeping it in the matrix.

Remove Python 3.5 as it is EoL-ed and add in Python 3.8 and 3.9.

Update Django User attributes

Closes uis/devops/ssgw/webapp#255 and uis/devops/ssgw/webapp#251

See merge request !19

Error when group with leading zeroes validated

Closes #12

See merge request !16

group id if it had leading zeroes. Removed the conversion of the id
to an int when passing to get_or_create_group_by_groupid(). Unnecessary
as the id was already validated with a regex.

The tests require a connection to the live lookup server

Closes #13

See merge request !15

invoke_method to return lookup results expected by the tests.

Missing feature: a user/group cannot be selected twice.

Closes #15

See merge request !14

Missing feature: a "self" selection should be locked

Closes #14

See merge request !13

So we implement it ourselves by filtering out pre-selected items in the
processResults callback.

solution suggested on stack overflow - namely, as each selection tag is
rendered add a custom class if it's the principle user.

Relevant posts:
  https://stackoverflow.com/questions/16564425/how-to-implement-select2-with-lock-selection/48111387#48111387
  https://jsfiddle.net/o3s3y42e/4/

Upgrade to use select2 version 4.

Closes #11

See merge request !12

Also refactored validate_crsids() into validate_crsids() and
validate_crsid_list().

style of both the container and dropdown elements of both the user and
group controls. See https://select2.org/configuration/options-api
and *CssClass.

crsids. Also added method convert_query_dict(query_dict): works around
the problems django has with validating a request parameter array.

This is a breaking change and the upgrade path will be detailed in the
README. However the main change is that the consumer will need to use
<select> instead of <input>.

Update Select2 (to latest v3) and jQuery libraries

Closes #11

See merge request !11