Also removed some dead and commented code around the edited area.

Note: `recursiveClustering'` was not actually recursive, it just went
one level deeper.

Upgrade 'haskell-bee' version, also bump up versions of some packages

See merge request !377

Resolve "Fix test build warnings"

See merge request !376

Also, add -Werror to tests so that no warnings in tests are reported anymore.

Switch to OpenAPI3 from Swagger2, to use proper Bearer token

Closes #427

See merge request !369

This commit adds three major tags to the swagger UI:

* Gargantext (like before): this spells out all the endpoints;
* Private operations: lists private backend ops;
* Public  operations: lists public backend ops.

More can be added, but the machinery used here should serve as a
blueprint.

OpenAPI3 will allow us to properly pass the Bearer Auth to the servant
swagger UI.

I fixed those warnings that were easy to fix: redundant imports, unused
variables, etc. (I might have missed some though)

The warnings I deliberately left for now are:
* In `Test.API.UpdateList`: Incomplete pattern matching (we would need
  to think a bit about error handling to fix this)
* In `Test.Utils`: `traceShowId` remains in code (we would need to think
  a bit about proper logging to fix this)

Resolve "Refactor `Gargantext.Database.Prelude`"

Closes #421

See merge request !372

Those definitions felt very ad hoc, and were not used a lot in the
codebase, so I simply replaced them with their definition.

Resolve "Job workers & persistence"

See merge request !371

This reverts commit ff00345c