Event needs extra fields

[casiepa]

The WPTV moderators are synchronizing the videos from WordPress.tv (currently with a tool outside of WordPress.tv, but to be integrated one day).

An event on WPTV (e.g. WordCamp Helsinki 2017) becomes a playlist on YouTube (e.g. ​https://www.youtube.com/playlist?list=PL1pJFUVKQ7EQLYwB4Ci4-YH-8jnfiqTG0)

To keep the overview, the current taxonomy 'event' would need some extra custom fields:

• YouTube playlist id
• w.org usernames of the organizers or people in charge of the videos
• slack usernames of the organizers or people in charge of the videos
• event hashtag

The usernames could be comma or space separated but a plain string is fine
The event hashtag will be used on social media

The event normally gets edited on ​https://wptv.wordpress.com/wp-admin/term.php?taxonomy=event&tag_ID=582334945

[dd32]

In 8378:

WordPress.TV: Add some custom fields for the Event taxonomy.

These are not exposed anywhere currently, but playlist & hashtag should be treated as public information.

Fixes #3913.