Added featured owners to featured scenarios

[louispt1]

I've added a migration and some minor changes to list a featured scenario owner alongside the featured scenarios in place of the current 'last updated at' attribute listing.

To note: The migration grabs the 'first' owner of a scenario as the default 'featured_owner'. This will need to be updated for our featured scenarios. For future featured scenarios, there is an input in the form to add the featured_owner.

I haven't done anything about the styling of the featured scenarios form because it's internal, but it would probably be good to pick that up at some point as the form (particularly for editing a featured scenario) is not pleasant to look at.

Closes #4156

[mabijkerk]

Looks good in the front-end. I like it! I haven't looked at the code. It seems that there are two open to-do's:

• [ ] Semaphore fails, I haven't checked why
• [ ] The featured owners need to be adjusted. I can pick this up @noracato / @louispt1 I suppose this is something that should be done manually on beta and pro db right?

[louispt1]

@noracato I'm going to pick up these suggested changes alongside some other upgrades to this PR that we discussed in the m&d meeting (like swapping the display order of the featured scenarios so most recent ones come first)

[louispt1]

@noracato I fixed the schema encoding issues and renamed to author, as well as changing the date to just be the year for the featured scenarios. Featured scenarios also now appear in order of most recent to least recent. I also updated the syntax according to your suggestions and updated the spec so it passes now! Let me know if you think any further changes are required.

P.s. I kind of assume we're better off using unicode_ci rather than 0900_ai_ci because it is more compatible with older versions of MySQL? Let me know if you disagree / have thoughts on this.

charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
charset: "utf8mb4", collation: "utf8mb4_unicode_ci", force: :cascade do |t|