Introduced `get|post` `/passreset` routes. These routes mimic the
behavior of the existing PHP implementation, with the exception of
HTTP status code returns.

Routes added:
    GET /passreset
    POST /passreset

Routers added:
    aurweb.routers.accounts

* On an unknown user or mismatched resetkey (where resetkey must ==
  user.resetkey), return HTTP status NOT_FOUND (404).
* On another error in the request, return HTTP status BAD_REQUEST (400).

Both `get|post` routes requires that the current user is **not**
authenticated, hence `@auth_required(False, redirect="/")`.

+ Added auth_required decorator to aurweb.auth.
+ Added some more utility to aurweb.models.user.User.
+ Added `partials/error.html` template.
+ Added `passreset.html` template.
+ Added aurweb.db.ConnectionExecutor functor for paramstyle logic.
  Decoupling the executor logic from the database connection logic
  is needed for us to easily use the same logic with a fastapi
  database session, when we need to use aurweb.scripts modules.

At this point, notification configuration is now required to complete
tests involved with notifications properly, like passreset.
`conf/config.dev` has been modified to include [notifications] sendmail,
sender and reply-to overrides. Dockerfile and .gitlab-ci.yml have been
updated to setup /etc/hosts and start postfix before running tests.

* setup.cfg: ignore E741, C901 in aurweb.routers.accounts

These two warnings (shown in the commit) are not dangerous and a bi-product
of maintaining compatibility with our current code flow.

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