Bug #1827747 Contrast on warning messages

Contrast on warning messages is not high enough due to bootstrap
default calculations, added overrides that are same as statuses.
Links in warning messages are also changed to bold.

behatnotneeded

Change-Id: I6e2632c74acf1afb75668c30409ada6381810fe3

htdocs/theme/raw/sass/form/_alert.scss

@@ -35,6 +35,9 @@
             }
         }
     }
+    a {
+        font-weight: bold;
+    }
 }
 
 .alert-default {
@@ -43,6 +46,27 @@
     color: $gray-500;
 }
 
+// overrides bootstrap calculations so this is same as states
+.alert-success {
+    color: scale-color($success, $lightness: -30%);
+    background-color: scale-color($success, $lightness: 70%);
+    border-color: scale-color($success, $lightness: 50%);
+}
+.alert-info {
+    color: scale-color($info, $lightness: -30%);
+    background-color: scale-color($info, $lightness: 70%);
+    border-color: scale-color($info, $lightness: 50%);
+}
+.alert-warning {
+    color: scale-color($warning, $lightness: -40%);
+    background-color: scale-color($warning, $lightness: 85%);
+    border-color: scale-color($warning, $lightness: 50%);
+}
+.alert-danger {
+    color: scale-color($danger, $lightness: -30%);
+    background-color: scale-color($danger, $lightness: 70%);
+    border-color: scale-color($danger, $lightness: 50%);
+}
 .alert-submitted {
     background-color: $state-submitted-bg;
     border: 1px solid $state-submitted-border;