New blog won't onebox

[simonb (Simon - Community Manager at Sphere)]

@eviltrout hope it’s OK to tag you as I see you worked on this before.

Is this still the correct user agent header that I can send to Medium support?

Onebox user agent

This commit adds a custom User-Agent to discourse oneboxes: https://github.com/discourse/discourse/commit/8bc93c0b018045bf23769b8ecc4ec5b493368667 The User agent looks like this: Discourse Forum Onebox v1.8.0.beta13