Make mailto: URLs matching stricter

So that it doesn't hit when an email-like construct occurs inside a URL.

Quotient/util.cpp

@@ -32,10 +32,8 @@ void Quotient::linkifyUrls(QString& htmlEscapedText)
  QStringLiteral(
  R"(\b((www\.(?!\.)(?!(\w|\.|-)+@)|(https?|ftp):(//)?\w|(magnet|matrix):)(&(?![lg]t;)|[^&\s<>'"])+(&(?![lg]t;)|[^&!,.\s<>'"\]):])))"),
  RegExpOptions);
- // email address:
- // [word chars, dots or dashes]@[word chars, dots or dashes].[word chars]
  static const QRegularExpression EmailAddressRegExp(
- QStringLiteral(R"(\b(mailto:)?((\w|\.|-)+@(\w|\.|-)+\.\w+\b))"),
+ QStringLiteral(R"((^|[][[:space:](){}`'";<>])(mailto:)?((\w|[!#$%&'*+=^_‘{|}~.-])+@(\w|\.|-)+\.\w+\b))"),
  RegExpOptions);
  // An interim liberal implementation of
  // https://matrix.org/docs/spec/appendices.html#identifier-grammar
@@ -49,7 +47,7 @@ void Quotient::linkifyUrls(QString& htmlEscapedText)
  // NOTE: htmlEscapedText is already HTML-escaped! No literal <,>,&,"
 
  htmlEscapedText.replace(EmailAddressRegExp,
- R"(<a href='mailto:\2'>\1\2</a>)"_ls);
+ R"(\1<a href='mailto:\3'>\2\3</a>)"_ls);
  htmlEscapedText.replace(FullUrlRegExp, R"(<a href='\1'>\1</a>)"_ls);
  htmlEscapedText.replace(MxIdRegExp,
  R"(\1<a href='https://matrix.to/#/\2'>\2</a>)"_ls);