Bug 33820: Add hints to warn the librarian that they will be logged out if they change their username

This patch adds some JavaScript to the patron entry form which adds a
hint if the logged-in librarian tries to change their own username. It
warns them that they will be logged out.

To test, apply the patch and log into the staff interface.

- Locate and edit your own patron record.
- In the "OPAC/Staff interface login" section, change the value in the
  username field. When focus leaves that form field a hint should
  appear, "You will be logged out if you modify your username."
- Change the username field back to your original username. The hint
  should disappear.
- Confirm that submitting a username change works correctly: You should
  be logged out, and when you log in again your username should be
  updated.

Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 8e611b79f1)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

koha-tmpl/intranet-tmpl/prog/en/modules/members/memberentrygen.tt

@@ -1867,6 +1867,16 @@ legend:hover {
             $("#categorycode_entry").on("change", function(){
                 update_category_code(this);
             });
+
+            [% IF logged_in_user.borrowernumber == borrowernumber %]
+                $("#userid").on("change", function(){
+                    $(this).parent().find("div.hint").remove();
+                    if ( "[% borrower_data.userid | html %]" != $(this).val() ) {
+                        $(this).parent().append('<div class="hint">%s</div>'.format(_("You will be logged out if you modify your username")));
+                    }
+                });
+            [% END %]
+
         });
 
         [% IF quickadd && opadd  && !check_member %]