[bw_group] shortcode to count the occurrences of a particular field value

[bobbingwide]

WordPress provides functions such as wp_list_categories() which provides counts of the total number of items in a particular taxonomy by category term. I need to be able to summarise the number of posts with a particular value. e.g. For the custom post type "competitor" there is a taxonomy of playing status. I want to be able to display the total number of competitors for an event by status.
e.g. Yes 19, No 3, TBC 4

Proposed solution

Develop a new shortcode called [bw_group] that will display the results of the query, summarising by the possible or discovered values depending on the grouping field's field type.

e.g.
[bw_group post_type='competitor' meta_key=_event meta_value=123 field='playing_status']

[bobbingwide]

The first draft of this change has been developed. So far it's only been tested counting taxonomy terms.