Open graph image path needs to be customisable

[kr8n3r]

At the moment the image in the template is set to
<meta property="og:image" content="/assets/images/govuk-opengraph-image.png">
and it doesnt resolve to the hostname.

As it's outside the head block so you have to define it in the head block again, but then you get two instances.

[NickColley]

A work around for this is to do:

{% block head %}
<meta property="og:image" content="your-path-here/assets/images/govuk-opengraph-image.png">
{% endblock %}

Since this will duplicate and override the default.