allow to change logo. default color for flash msg

- two new environment variables allow to change logo background color
  and graphic
- flash messages are now green (not cyan)

core/admin/mailu/configuration.py

@@ -56,6 +56,8 @@ DEFAULT_CONFIG = {
     'WEBMAIL': 'none',
     'RECAPTCHA_PUBLIC_KEY': '',
     'RECAPTCHA_PRIVATE_KEY': '',
+    'LOGO_URL': None,
+    'LOGO_BACKGROUND': None,
     # Advanced settings
     'LOG_LEVEL': 'WARNING',
     'SESSION_KEY_BITS': 128,

core/admin/mailu/ui/templates/base.html

@@ -45,8 +45,8 @@
         </ul>
       </nav>
       <aside class="main-sidebar sidebar-dark-primary nav-compact elevation-4">
-        <a href="{{ url_for('.domain_list' if current_user.manager_of or current_user.global_admin else '.user_settings') }}" class="brand-link bg-primary">
-          <img src="{{ url_for('.static', filename='mailu.png') }}" width="33" height="33" alt="Mailu" class="brand-image mailu-logo img-circle elevation-3">
+        <a href="{{ url_for('.domain_list' if current_user.manager_of or current_user.global_admin else '.user_settings') }}" class="brand-link bg-mailu-logo"{% if config["LOGO_BACKGROUND"] %} style="background-color:{{ config["LOGO_BACKGROUND"] }}!important;"{% endif %}>
+          <img src="{{ config["LOGO_URL"] if config["LOGO_URL"] else url_for('.static', filename='mailu.png') }}" width="33" height="33" alt="Mailu" class="brand-image mailu-logo img-circle elevation-3">
           <span class="brand-text font-weight-light">{{ config["SITENAME"] }}</span>
         </a>
         {%- include "sidebar.html" %}
@@ -66,7 +66,7 @@
           </div>
         </section>
         <div class="content">
-          {{ utils.flashed_messages(container=False) }}
+          {{ utils.flashed_messages(container=False, default_category='success') }}
           {%- block content %}{%- endblock %}
         </div>
       </div>