Review and possibly combine pages covering access control and secrets

[louzoid-gds]

We have several pages covering similar themes:

On access control:

• Tracking access control
• Principle of least privilege
• How to manage access to you third-party service accounts

On looking after credentials & secrets:

• How to store credentials
• Secret auditing

The guidance on these pages is interlinked and occasionally repetitive. Therefore, it may be useful to review, rewrite and combine the guidance into a single page (Access control & secrets) or two pages instead of the existing five.

The new page(s) should also link out to relevant parts of the NCSC Cyber assessment framework and existing good practice in GDS.