[FIX] mail: no link special character mention

When we mention for example `@hell'o`, the user will be added as
subscriber but he is not linked.

This is because there is two part of mentions:

- inserting the mention in the message: at this point the mention is
  not escaped (only space are replaced with non-breaking space).

- wrapping a link around the mention in a message that is being posted:
  at this time the message has been escaped ( for &<>"`' ).

Thus when wrapping the mention, we have to search the escaped content.

In the case of canned response, the system is different with defined
substitution that replaced the "shortcut" so this makes no change to
that.

Added test without fix failed with:

8. should contain a link in the message content (expected:1, result:0)
9. should have correct mention link in the message content
    (expected:"@ЅpëciãlUser<&>\"`' ツ", result: "")

opw-1909300
closes #28846

0 files changed, 0 insertions, 0 deletions