Cookie banner form element should have a (universal) ID

[jonoalderson]

We're iterating on our analytics setup for WordCamp websites, and want to understand form interactions in particular.

However, the cookie policy acceptance form currently pollutes that data, in a way that's hard to filter. Adding a simple id parameter to the current markup (with a simple/consistent value) would help us to significantly improve our understanding of what's going on on these sites.

[pkevan]

Updated Jetpack to 13.6, and the id now appears on the form 🥳