Issue #3255681: Purge / Purge UI integration

[johnbburg]

Adds purge integration

Just an initial patch, but I am already using it on a site. It appears to successfully purge static files via the pantheon CDN via a curl request with a unique parameter (I was told this works in a support ticket, and it does seem to for me).

[johnbburg]

Any thoughts on this patch?

[johnbburg]

Was just looking at this problem today, It seems that someone has commented in the Drupal module issue that started this referencing another issue that accomplishes this by clearing all the CDN when a file is uploaded.

It seems that the function pantheon_clear_edge_paths() is available, but isn't well documented outside of it appearing in a couple of examples in documentation (here and here) . Clearing the full CDN cache isn't ideal though, and the hesitation to use the pantheon_clear_edge_paths() was due to it's lack of documentation. Can someone confirm if it's appropriate to use in these instances?

I think it's still worthwhile to integrate with the existing purge ecosystem however. So perhaps this PR can be amended to use that function?

Could we also clarify how issues should be filed against this project? I posted this issue in here like the module instructions state, and it's ignored for 2 years. Someone makes a GitLab PR, and it was merged within a month.