add /tu/ (get) index

This commit implements the '/tu' Trusted User index page.

In addition to this functionality, this commit introduces
the following jinja2 filters:

- dt: util.timestamp_to_datetime
- as_timezone: util.as_timezone
- dedupe_qs: util.dedupe_qs
- urlencode: urllib.parse.quote_plus

There's also a new decorator that can be used to enforce
permissions: `account_type_required`. If a user does not
meet account type requirements, they are redirected to '/'.

```
@auth_required(True)
@account_type_required({"Trusted User"})
async def some_route(request: fastapi.Request):
    return Response("You are a Trusted User!")
```

Routes added:

- `GET /tu`: aurweb.routers.trusted_user.trusted_user

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

templates/tu/index.html

@@ -0,0 +1,35 @@
+{% extends "partials/layout.html" %}
+
+{% block pageContent %}
+    {%
+        with table_class = "current-votes",
+        total_votes = current_votes_count,
+        results = current_votes,
+        off_param = "coff",
+        by_param = "cby",
+        by_next = current_by_next,
+        title = "Current Votes",
+        off = current_off,
+        by = current_by
+    %}
+        {% include "partials/tu/proposals.html" %}
+    {% endwith %}
+
+    {%
+        with table_class = "past-votes",
+        total_votes = past_votes_count,
+        results = past_votes,
+        off_param = "poff",
+        by_param = "pby",
+        by_next = past_by_next,
+        title = "Past Votes",
+        off = past_off,
+        by = past_by
+    %}
+        {% include "partials/tu/proposals.html" %}
+    {% endwith %}
+
+    {% with title = "Last Votes by TU", votes = last_votes_by_tu %}
+        {% include "partials/tu/last_votes.html" %}
+    {% endwith %}
+{% endblock %}