External link regex for approval matches internal domains

[mdashlw]

philomena/lib/philomena/schema/approval.ex

Line 12 in b7a95ee

"https?\\\\?:(?:\\\\*\\/?)*(?!(?:#{Enum.map_join(site_domains, "|", &Regex.escape/1)}))"

My attempts at dealing with autolink behavior broke the negative lookahead