Add business justification free-text field to the form for requesting namespace access and response from administrator

[ghost]

The form to request access to a namespace does not share much data with the namespace administrator(s) once a request is sent. It is a somehow difficult balance between sending as little data as possible and having a functioning access request system. It could be improved by adding an optional, free-text area to the request form, so the requesting user could convey a personal message to any administrator the message reaches.

This data would not be persisted by Vorto in any way just like the rest of the request, and sent directly to the administrator if any eligible (read: any has an e-mail set).

Conversely, the administrator could send a response when processing the request in Vorto, that would convey a message to the requesting user regardless of whether the request was approved as is, approved with different roles or rejected.

Might require some refinement / brainstorm / legal advice before implementing.