Docs: Fix status reporting to throw on error

[IanButterworth]

Doc deploy is currently broken, but hasn't been throwing. Dev docs may be quite out of date.

A post_status method was missing for the build bot config, meaning that on an error status no error was thrown and just the fall back method that returns nothing.

This is evident because the DOCUMENTER_KEY appears to be broken in the build system but was just being printed as an @error in a successful make deploy step? @fredrikekre / @staticfloat ?

This adds throws on "errored" or "failed" status so the build system can catch it.

cc. @mortenpi

[mortenpi]

I'd say this LGTM, but it might be good to hear if @fredrikekre sees any issues with this.

[fredrikekre]

Why doesn't deploydocs error instead?

[IanButterworth]

I believe it's because on GitHub actions there's more granularity than just success or fail, so the error is logged and post_status sets the api endpoints appropriately.

Making post_status do the throwing seems like the right way to do with how the dispatching is set up.

I defer to @mortenpi though.

[mortenpi]

Doing the dispatch here allows us to fix the problem without having to make changes to Documenter.

But yea, arguably deploydocs should just throw too actually, since I think that part shouldn't fail unless there is a network or configuration problem.

[fredrikekre]

JuliaDocs/Documenter.jl#1529 is better I think

[mortenpi]

I would like to put JuliaDocs/Documenter.jl#1529 into a minor release though, which will probably be a while, so it might be worth merging this as is and removing it when we update Documenter to 0.27 here.

[fredrikekre]

Fixed in Documenter.