Private note on User

[RignonNoel]

As an administrator we often need to keep some notes on each users to be able to remember important fact or to keep information updated between staff member.

However most of the time we like to have privacy on this note to be able to put pseudo-sensitive information and write freely.

Expected behavior

• Administrators can add a private note on User
• Administrators can update the private note of User

Current behavior

It's a new feature, we have no way to do that actually

Potential solution

• Add a new private_note field on User
• Update serializer to be sure the private note is visible only by the staff