It turns out that we don't need to call `pruneForest` inside
`searchtableNgrams`. After all, we are just displaying information that
should be correct in the database from the get-go, so why we would need
any of that?

It turns out that the fix for #313 to support duplicated ngrams during
importing broke hierarchical grouping.

I have just temporarily commented out the code and I need to find a fix,
better also writing a test to ensure that grouping will still work in the
future.

This function allows us to keep only the roots, and discard the
redundant children after building a 'Forest'.

I think we can use the NgramsTree and NgramsForest types to our
advantage for the 'searchTableNgrams' & co, so I have revamped that
module to put it to good use.

This commit changes the implementation of filterNgramsNodes to not
filter too aggressively nodes that are present in a path.

This causes a test failure that needs to be investigated.

[openalex] make search act similar to the one on openalex web

See merge request !425

Port all the tasty specs to hspec

See merge request !423

See #490

Resolve "Error uploading zip file on dev"

See merge request !417

Fix bug in DB transaction rollbacks in the presence of domain-specific errors

Closes #480

See merge request !420

This commit fixes the bug with DbTx rollbacks and domain-specific
errors. What we do now is throwing an exception during the evaluation of
`DbFail`, to later catch it _after_ `withTransactionM` has performed a
clean rollback, and only at that point we call `throwError`.

This also means that we need to catch `DbTx` errors via the `MonadError`
interface, not via the exception-handling interface, to get proper
rollback behavior.

errorWith has a `HasNodeError` constraint but the name was misleading.

This means, of course, that now rollback tests are failing, but that's
fine, we can then fix things properly in the DbTx code.

Have `extractNgramsFromDocument` catch the right exception in case extraction fails

Closes #481

See merge request !419

[graphql] get contexts for ngrams fix

See merge request !416

Resolve "API refactorings"

See merge request !412