Refactor Middleware.hs

[wolfgangwalther]

This refactoring increases coverage in Middleware.hs. We still need to add some tests for the error logging part, but this will have to wait until #1717 is merged, so we don't get too many merge conflicts on the IO tests. The haskell stuff is ready for review.

I did:

• Refactor the logger middleware avoiding the re-implementation of the upstream apache logger
• Refactor the CORS policy, where the settings were spread out across two functions. Seems like the incorrect Authentication header has been used here so far, too, which should be Authorization. In fact Authorization was used in "defaults", but was immediately overwritten in the other function with Authentication, so never used. Reformatted the test cases here, too.
• Added a few extra claims to the role claims tests, to increase test coverage in the runPgLocals function.

TODO:

• Add logging tests

[wolfgangwalther]

Based on #2111 now - need to figure out why those tests are red. After that, this should be good to merge.

[wolfgangwalther]

The loadtest is expected to fail, because it can't deal with removing dependencies in postgrest.cabal. This is because, the nix environment is started on the PR branch, but during postgrest-loadtest-against the main branch is checked out. The main branch will then try to find the now-removed dependency... but can't, because nix doesn't provide it.