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>

aurweb/asgi.py

@@ -16,7 +16,7 @@ from aurweb.auth import BasicAuthBackend
 from aurweb.db import get_engine, query
 from aurweb.models.accepted_term import AcceptedTerm
 from aurweb.models.term import Term
-from aurweb.routers import accounts, auth, errors, html, sso
+from aurweb.routers import accounts, auth, errors, html, sso, trusted_user
 
 # Setup the FastAPI app.
 app = FastAPI(exception_handlers=errors.exceptions)
@@ -47,6 +47,7 @@ async def app_startup():
     app.include_router(html.router)
     app.include_router(auth.router)
     app.include_router(accounts.router)
+    app.include_router(trusted_user.router)
 
     # Initialize the database engine and ORM.
     get_engine()