Previously, it was only possible to update a single query parameter with

{% querystring_with %}. However, in the name of future proofing, it 

became necessary to make a new template tag {% querystring %} 

that can take an arbitrary number of key-value pairs now with different 

modes in the form of:
{% querystring “mode” "key1=value1" "key2=value2" %}
The three different modes are:

“remove” - Will remove keys from the query string.

“append” - Will append values for its given key without overwriting.

“update” - Will add to or replace part of a query string.

Ran unit tests.