add fastly detection

[dolevf]

Which category is this pull request?

• A new feature/enhancement.
• Fix an issue/feature-request.
• An improvement to existing modules.
• Other (Please mention below).

Where has this been tested?

• Python Version
  • v3.x
  • v2.x
• Operating System:
  • Linux (Please specify distro)
  • Windows
  • MacOS

Does this close any currently open issues?

#234

Does this add any new dependency?

No

Does this add any new command line switch/argument?

No

Any other comments you would like to make?

Logic to detect Fastly WAF Is baesd on the Fastyl's documented X-Served-By header
https://www.fastly.com/documentation/reference/http/http-headers/X-Served-By/

[sandrogauci]

The regex could be tightened to match Fastly's specific naming convention:

  # Current (broad):
  r'^cache-[^\s]*'

  # More specific to Fastly's format:
  r'^cache-[a-z]{3}\d+-[A-Z]{3}'

This would reduce false positives from generic Varnish setups while still catching Fastly's distinctive cache server naming.

[sandrogauci]

thanks for that @dolevf