This initial work adds a pair of settings to configure specific CSP
directives for enforcing or reporting policy violations, a new
`django.middleware.csp.ContentSecurityPolicyMiddleware` to apply the
appropriate headers to responses, and a context processor to support CSP
nonces in templates for safely inlining assets.
Relevant documentation has been added for the 6.0 release notes,
security overview, a new how-to page, and a dedicated reference section.
Thanks to the multiple reviewers for their precise and valuable feedback.
Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>