"Logged in as: XXX - logout" navigation item

[simonw]

Originally posted by @simonw in #840 (comment)

[simonw]

I could borrow the implementation for this from datasette-auth-github
https://github.com/simonw/datasette-auth-github/blob/182298b034ecb647971b65057d1d3e7b7fbbb482/datasette_auth_github/templates/base.html

{% extends "default:base.html" %}

{% block extra_head %}
<style type="text/css">
.hd .logout {
    float: right;
    text-align: right;
    padding-left: 1em;
}
</style>
{% endblock %}

{% block nav %}
    {{ super() }}
    {% if auth and auth.username %}
        <p class="logout">
            <strong>{{ auth.username }}</strong> &middot; <a href="/-/logout">Log out</a>
        </p>
    {% endif %}
{% endblock %}

[simonw]

From #840 (comment)

Another problem: what to display in the "you are logged in as", since we don't dictate an actor design.

I'm going to use a includes template for this that can easily be over-ridden by administrators or by plugins.

The default will look for the first available of the following keys:

* display
* name
* username
* login
* id

[simonw]