caddyhttp: Return HTTP 421 for mismatched Host header (#4023)
caddyhttp: Return HTTP 421 for mismatched Host header (#4023)

Potential fix for #4017 although the consensus is unclear.

Made change to return status code 421 instead of 403 when StrictSNIHost matching is on.
mholt/caddy,l3dlp/caddy,l3dlp/caddy,l3dlp/caddy,mholt/caddy