Change homepage shelf api response to use similar CTA style object #8214
Description
https://addons-server.readthedocs.io/en/latest/topics/api/shelves.html#homepage-shelves returns footer_text and footer_pathname
results[].footer_text (string|null) – The optional text in the footer of the shelf.
results[].footer_pathname (string|null) – The optional pathname of the URL for the footer’s text.
Which are really pretty similar to the cta object returned in the secondary hero shelf (and modules). For code reuse (both in addons-server and addons-frontend) lets change the homepage shelf response to be
results[].footer (object|null) – The optional footer link and text for the shelf.
results[].footer.url (string) – The url the call to action would link to.
results[].footer.outgoing (string) – url wrapped with outgoing (See Outgoing Links)
results[].footer.text (object|null) – The call to action text.
(bonus outgoingifying if we ever want to allow external linking)