Add subsites cache context.

[rupertj]

Thanks for this - it's nice to see the start of being able to override the branding :)

One thing I'm wondering is if the name of the context properly reflects what it is. Currently it's just "subsites" and it returns the value of the current subsite theme.

I'm thinking it could be better to have "subsite" and "subsite.theme" as contexts, as you might feasibly want to have two different subsites using the same colour scheme, but with different logos. "subsite" could just use the nid of the root node as its value.

[Polynya]

I meant to point out that it uses the theme.

Following the patterns here: https://www.drupal.org/docs/drupal-apis/cache-api/cache-contexts I think we could have:

• subsites.homepage (subsites overview node id)
• subsites.theme (visual theme)
• subsites (I'm not sure but either of these?)

[rupertj]

Ok, let's go for that. I think subsites by itself should be the node id, so I'll implement it like that.

[rupertj]

@Polynya I've made the changes. Care to give it a review?

[Polynya]

Looks good to me, thanks