First shot at supporting custom handler

app/templates/custom_page.html

@@ -0,0 +1,30 @@
+{%- import "utils.html" as utils with context -%}
+{% extends "layout.html" %}
+
+{% block head %}
+<title>{{ title }}</title>
+{% if request.url.path == "/" %}
+<link rel="indieauth-metadata" href="{{ url_for("well_known_authorization_server") }}">
+<link rel="authorization_endpoint" href="{{ url_for("indieauth_authorization_endpoint") }}">
+<link rel="token_endpoint" href="{{ url_for("indieauth_token_endpoint") }}">
+<link rel="micropub" href="{{ url_for("micropub_endpoint") }}">
+<link rel="alternate" href="{{ local_actor.url }}" title="ActivityPub profile"  type="application/activity+json">
+<meta content="profile" property="og:type" />
+<meta content="{{ local_actor.url }}" property="og:url" />
+<meta content="{{ local_actor.display_name }}'s microblog" property="og:site_name" />
+<meta content="Homepage" property="og:title" />
+<meta content="{{ local_actor.summary | html2text | trim }}" property="og:description" />
+<meta content="{{ local_actor.url }}" property="og:image" />
+<meta content="summary" property="twitter:card" />
+<meta content="{{ local_actor.handle }}" property="profile:username" />
+{% endif %}
+{% endblock %}
+
+{% block content %}
+{% include "header.html" %}
+
+<div class="box">
+    {{ page_content | safe }}
+</div>
+
+{% endblock %}