Bug 37732: Update templates to use Bootstrap styles when alert class comes from the...

Bug 37732: Update templates to use Bootstrap styles when alert class comes from the perl script

Many pages can have alerts that get their style from a variable passed
by the script, e.g.:

push @messages, { type => 'message', code => 'success_on_update' };

Rather than change these to match Bootstrap 5 styles, I propose we add a
copy of the existing Bootstrap style using the existing vocabulary:

message -> info
alert  -> warning
error -> danger

To test, apply the patch and rebuild CSS for the staff interface and
OPAC: (https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_interface)

- Clear your browser cache if necessary.
- Navigate to pages which have been updated by this patch. Many pages
  will implement this kind of alert after saving an edit, especially
  administration pages, e.g.

  Administration -> Libraries -> Edit library -> Save.

- You can test the various alert classes by adding this HTML to
  IntranetMainUserBlock and OpacMainUserBlock and viewing the staff
  interface and OPAC main pages.:

<div class="alert alert-danger">A standard Bootstrap danger alert with
  <a href="#" class="alert-link">an example link</a>.</div>
<div class="alert alert-warning">A standard Bootstrap warning alert with
  <a href="#" class="alert-link">an example link</a>.</div>
<div class="alert alert-info">A standard Bootstrap info alert with
  <a href="#" class="alert-link">an example link</a>.</div>
<div class="alert alert-error">A Koha error alert with
  <a href="#" class="alert-link">an example link</a>.</div>
<div class="alert alert-alert">A Koha alert alert with
  <a href="#" class="alert-link">an example link</a>.</div>
<div class="alert alert-message">A Koha info alert with
  <a href="#" class="alert-link">an example link</a>.</div>

Sponsored-by: Athens County Public Libraries
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>