Add rake task to find pages with missing search content
Add rake task to find pages with missing search content

Identify pages in finders which have missing search content. Specialist
documents have a hidden field named `hidden_indexable_content` which is
used just for search indexing, but this data is missing from Rummager
for many documents. This rake task finds those documents so that they
can be republished.

This rake task should be deleted once the missing data has been added.

alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild