Add SOP for XNAT access requests

[heyhaleema]

We should add an SOP for XNAT access requests to the repo and ideally, the CSC website as well. This could also be included in/based on the QMS repo and as a template on this repo.

I think this should include details required in the initial access request, any required training and information governance, and the applicable role-based access control (RBAC).

For example:

• Which project(s) does the request cover?
• What are the contact details of the user?
• How long is access required?
• What type of data is required?
• What is the volume of data required?
• What is the expected access frequency/schedule?