Add unit tests to create and verify base url permutations.

[jamwil]

Unit tests to verify that a site::Site is successfully built and contains valid permalinks using the new base url logic in src/cmd/serve.rs introduced in #2311.

Closes #2448.

I am marking this as a draft for now. This tests the create_new_site function and verifies the urls and paths, but I'd like to add further tests of the actual live hyper endpoint.

Edit: Not sure the hyper endpoint tests are important at this stage.

Note that the tests will fail until this rebased on #2482 as that PR makes the trailing slash behaviour consistent with prior before we added the construct_base_url function.

Sanity check:

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Code changes

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If the change is a new feature or adding to/changing an existing one:

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[Keats]

If you rebase is it ok to merge?

[jamwil]

@Keats Hey Vincent, my apologies—was on a long trip, followed by a large backlog resulting from said long trip.

Yes, I think this is ok to merge—these tests are adequate for our purposes as outlined in #2448. I'll rebase shortly (today or tomorrow). Thanks.

[jamwil]

@Keats Good to merge, mate. Cheers.

[Keats]

Looks like this fails on windows?

[jamwil]

All the tests were green prior to rebase. The process cannot access the file because it is being used by another process. This seems like a concurrency issue with the test runner.

[jamwil]

Can we try re-running and see if it was transient?

[Keats]

looks good!

[Keats]

It does fail very often on CI in the end, I'll disable it for windows

[jamwil]

Well that's unfortunate. I have a Windows VM I'll see if I can reproduce the failure outside of CI.

[jamwil]

It is peculiar if it only fails on the one test you disabled as there are several that are virtually identical, just using slightly different parameters.

I expect the failure to reemerge on the next active test of that type...

[Keats]

Yeah it's weird. I've disabled it so i can release 0.19 but it would be interesting to get some investigation done