workflows: hodingpen object history

* Adds the history of an object on the details page.

Signed-off-by: Guillaume Lastecoueres <guillaume.lastecoueres@cern.ch>
workflows: merging corrections

* Fixes import format.

* Fixes tests presentation.

* Fixes unit tests.

* Fixes PEP257.

* Fixes useless utf-8 conversion.

* Fixes _task_result type modification.

* Fixes python3 compatibility.

Signed-off-by: Guillaume Lastecoueres <guillaume.lastecoueres@cern.ch>