Link to user in wiki syntax only works when login is written in lower case
The plugin "Redmine Mentions" gives a handy dropdown with users when hitting "@" on the keyboard. Selecting a user puts "@loginname" in the textbox. This works great with the feature implemented in #4179. However, if the user's login contains capital letters it is not recognized by the regex in application_helper.
"Redmine mentions" puts in the actual login-name with exact casing (what I believe is the correct behaivour).
The regex should be ajusted to a-zA-Z