feat(FastAPI): added /requests (get) route

Introduces `aurweb.defaults` and `aurweb.filters`.

`aurweb.filters` is a location developers can put their additional
Jinja2 filters and/or functions. We should slowly move all of our
filters over here, where it makes sense.

`aurweb.defaults` is a new module which hosts some default constants
and utility functions, starting with offsets (O) and per page values
(PP).

As far as the new GET /requests is concerned, we match up here to
PHP's implementation, with some minor improvements:

Improvements:

* PP on this page is now configurable: 50 (default), 100, or 250.
    * Example: `https://localhost:8444/requests?PP=250`

Modifications:

* The pagination is a bit different, but serves the exact same purpose.
* "Last" no longer goes to an empty page.
    * Closes: https://gitlab.archlinux.org/archlinux/aurweb/-/issues/14

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_util.py

@@ -1,7 +1,7 @@
 from datetime import datetime
 from zoneinfo import ZoneInfo
 
-from aurweb import util
+from aurweb import filters, util
 
 
 def test_timestamp_to_datetime():
@@ -34,3 +34,9 @@ def test_to_qs():
     query = {"a": "b", "c": [1, 2, 3]}
     qs = util.to_qs(query)
     assert qs == "a=b&c=1&c=2&c=3"
+
+
+def test_round():
+    assert filters.do_round(1.3) == 1
+    assert filters.do_round(1.5) == 2
+    assert filters.do_round(2.0) == 2