File Uploads: Added basic validation response formatting

Tested via app-level validation file limit, and then also with nginx
file post limit.
For #4996

resources/js/components/dropzone.js

@@ -181,10 +181,7 @@ export class Dropzone extends Component {
                 if (this.readyState === XMLHttpRequest.DONE && this.status === 200) {
                     upload.markSuccess(component.successMessage);
                 } else if (this.readyState === XMLHttpRequest.DONE && this.status >= 400) {
-                    const content = this.responseText;
-                    const data = content.startsWith('{') ? JSON.parse(content) : {message: content};
-                    const message = data?.message || data?.error || content;
-                    upload.markError(message);
+                    upload.markError(window.$http.formatErrorResponseText(this.responseText));
                 }
             },
         });

resources/js/services/http.js

@@ -207,3 +207,32 @@ async function performDelete(url, data = null) {
 }
 
 export {performDelete as delete};
+
+/**
+ * Parse the response text for an error response to a user
+ * presentable string. Handles a range of errors responses including
+ * validation responses & server response text.
+ * @param {String} text
+ * @returns {String}
+ */
+export function formatErrorResponseText(text) {
+    const data = text.startsWith('{') ? JSON.parse(text) : {message: text};
+    if (!data) {
+        return text;
+    }
+
+    if (data.message || data.error) {
+        return data.message || data.error;
+    }
+
+    const values = Object.values(data);
+    const isValidation = values.every(val => {
+        return Array.isArray(val) || val.every(x => typeof x === 'string');
+    });
+
+    if (isValidation) {
+        return values.flat().join(' ');
+    }
+
+    return text;
+}

resources/sass/_components.scss

@@ -321,6 +321,10 @@ body.flexbox-support #entity-selector-wrap .popup-body .form-group {
   background-color: var(--color-primary);
   transition: width ease-in-out 240ms;
 }
+.dropzone-file-item-label {
+  line-height: 1.2;
+  margin-bottom: .2rem;
+}
 .dropzone-file-item-label,
 .dropzone-file-item-status {
   align-items: center;