How to add a shortcode function that returns the taxonomy slug of the actual post within the loop

Circumstances: I have a CPT called “designs” and a taxonomy related to it, called “project_category” so that I can assign a category to each design. I’m building the template for each ‘design’ and I need a shortcode that returns the assigned project category SLUG of the current design within the loop.

What is the wordpress way of displaying local external content?

I have a somewhat tricky situation. A company’s internal server, running some unknown software (means I have no access whatsoever), exports data to my http server via a custom API. This data gets stored in the same MySQL environment as WordPress. Just a different DB. Meaning DB1 has the WP data, DB2 holds the imported company data.