Save "created by" in the backend

[virgile-dev]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
For the new UI we need to be able to filter documents that were created by the user.

Describe the solution you'd like
Save which user created the doc in the backend.

Discovery, Documentation, Adoption, Migration Strategy

[virgile-dev]

Solved with #429