Add blockId to trail meta

[jonathonherbert]

Adds an optional blockId property to our Trail objects.

Required to let facia-tool store block ids for breaking news notifications that refer to liveblogs, allowing notification clients to point the user to a specific block in a liveblog.

[ajwl]

NB: adding AtomId required a few more changes. Are we likely to require some more of these? https://github.com/guardian/facia-scala-client/pull/231/files

[jonathonherbert]

Great question, @ajwl -- going through those files,

• curatedcontent.scala -- we shouldn't have to worry about snaplinks, as this change only relates to articles
• FaciaContentUtils.scala -- there's nothing downstream that consumes the atomId yet (the notification client has its own model, BreakingNewsPayload) and without a use case I was reluctant to add code, so we should be fine for now (although open to opinions here!)
• Test files -- because the change was very simple, I didn't add a test, although I'm happy to do this

I hope that makes sense, and we can always revisit if necessary.

[ajwl]

👍 cool thanks for the update. Will proceed with this