Start a process using datasets

Refs https://redmine.teklia.com/issues/3653

The main goal is to create a new endpoint that allows a user to create a new process of type Dataset on a given corpus, using several datasets. This introduces the new ProcessMode.Dataset

The endpoint is named CreateDatasetProcess and uses these inputs:

• corpus ID
• multiple dataset IDs
  • ⚠ these datasets can be from different corpus, but at least one of them must be in the corpus mentionned before
• name (required for that endpoint)

You'll need to create a Many-to-Many relationship between Process and Dataset, no need to use a through model here.

No tasks should be created here, we absolutely want to manage worker runs manually afterwards. The endpoint must simply return the default serializer response for process along with the newly created process id.

Please make sure that you can also use CreateWorkerRun and StartProcess to update and then run this process.

Finally, you need to make sure datasets are updatable through PartialUpdateProcess and UpdateProcess.