Rationale:

• The db currently tracks “has_captcha”. Cloudflare influences that regardless of whether the site is itself configured to push a CAPTCHA.
• The db currently tracks “open_registrations”. The degree of openness depends on whether a node is on Cloudflare, regardless of how the software is configured.
• Checking for Cloudflare is free. That is, no extra connections are needed. It’s simply a matter of checking for the presence of CF-RAY in the http headers on existing fetches.
• The mission purpose of fediseer is to facilitate trust assessment. The use of Cloudflare is a significant factor in that regard.