DB seed script for development

[pablobm]

In order:

1. Extract the code of the oauth:register_apps task into a method, to allow reuse.
2. Use this to create initial users, including an admin.

This takes inspiration from @mmd's https://gist.github.com/mmd-osm/a3a0b5a8799a333e7fae578038aa7a93 and @gravitystorm's #3101 (which it would replace). We can think about adding more in the future.

[tomhughes]

If we're going to use db:seed to set things up then do we still need oauth:register_apps as well?

[pablobm]

I think that oauth:register_apps is still useful for people who don't through the bin/setup route, or if something goes wrong and the rake task still needs to be run.

[pablobm]

I have revisited this now, simplifying, moving the bin/yarn part out (will go in a separate PR), and putting it in a separate task dev:populate.

[pablobm]

Hm, I can't rename the PR (it still says "DB seed"). The "edit" button is missing. Has there been a recent change in permissions?

[tomhughes]

We haven't changed anything as far as I know but github might have done...

[tomhughes]

In addition to the inline comments I think there's probably scope here for tidying up the commit history as there seem to be cases here where later commits are fixing up earlier ones?

[pablobm]

Addressed the comments now 👍