Rename sf-discount-error to sf-cart-issue for cart validation messages.

The class is used for stock, discount, and cart-total issues—not only discounts.

backend/src/modules/storefrontCore/public/css/storefront.css

@@ -798,7 +798,7 @@ a:hover {
     margin: 0;
 }
 
-.sf-line-item__body > .sf-discount-error {
+.sf-line-item__body > .sf-cart-issue {
     margin: 0.125rem 0 0;
 }
 
@@ -875,7 +875,7 @@ a:hover {
     color: var(--sf-text-muted);
 }
 
-.sf-discount-error {
+.sf-cart-issue {
     margin: 0 0 var(--sf-space-2);
     font-size: 0.85rem;
     color: var(--sf-error);

backend/src/modules/storefrontCore/views/partials/cart-line-item.hbs

@@ -28,7 +28,7 @@
                 {{@root.shopFiatCurrency}}</div>
             <div class='sf-line-item__note'>{{> product-delivery-note deliveryMode=deliveryMode}}</div>
             {{#if stockIssueMessage}}
-                <p class='sf-discount-error'>{{stockIssueMessage}}</p>
+                <p class='sf-cart-issue'>{{stockIssueMessage}}</p>
             {{else}}
                 {{#unless stockForSession}}
                     <p class='sf-text-subtle'>No more in stock beside your order</p>
@@ -36,7 +36,7 @@
             {{/if}}
             {{#each @root.discounts}}
                 {{#if (includes ineligibleVariantIds ../id)}}
-                    <p class='sf-discount-error'>Not eligible for code {{code}}</p>
+                    <p class='sf-cart-issue'>Not eligible for code {{code}}</p>
                 {{/if}}
             {{/each}}
             <form class='sf-form-row' method='post' action='/shop/cart/product/update'>

backend/src/modules/storefrontCore/views/partials/cart-totals-panel.hbs

@@ -23,7 +23,7 @@
                         }}
                         <span class='sf-discount-row__code sf-text-error'>{{code}}</span>
                     </div>
-                    <p class='sf-discount-error'>{{issueMessage}}</p>
+                    <p class='sf-cart-issue'>{{issueMessage}}</p>
                 {{else if amount}}
                     <div class='sf-discount-row sf-discount-item'>
                         {{> dismiss-button
@@ -62,7 +62,7 @@
     </form>
 
     {{#if cartTotalIssueMessage}}
-        <p class='sf-discount-error'>{{cartTotalIssueMessage}}</p>
+        <p class='sf-cart-issue'>{{cartTotalIssueMessage}}</p>
     {{/if}}
 
     <div class='sf-stack sf-mt-4'>