Allow empty alt text for decorative images

src/main/java/uk/ac/cam/cl/dtg/isaac/dos/content/Media.java

@@ -26,6 +26,7 @@
 public abstract class Media extends Content {
     protected String src;
     protected String altText;
+    protected Boolean decorative;
 
     /**
      * Gets the src.
@@ -65,4 +66,23 @@ public void setAltText(final String altText) {
         this.altText = altText;
     }
 
+    /**
+     * Gets whether the media is decorative.
+     *
+     * @return whether the media is decorative
+     */
+    public Boolean getDecorative() {
+        return decorative;
+    }
+
+    /**
+     * Sets whether the media is decorative.
+     *
+     * @param decorative
+     *            whether the media is decorative
+     */
+    public void setDecorative(final Boolean decorative) {
+        this.decorative = decorative;
+    }
+
 }

src/main/java/uk/ac/cam/cl/dtg/segue/etl/ContentIndexer.java

@@ -977,8 +977,9 @@ public void recordContentTypeSpecificError(final String sha, final Content conte
                 }
             }
 
-            // check that there is some alt text.
-            if (f.getAltText() == null || f.getAltText().isEmpty()) {
+            // Check that there is some alt text. Decorative images should have empty alt text.
+            boolean isDecorative = null != f.getDecorative() && f.getDecorative();
+            if (f.getAltText() == null || (f.getAltText().isEmpty() && !isDecorative)) {
                 if (!(f instanceof Video) && !f.getId().equals("eventThumbnail")) {
                     // Videos probably don't need alt text unless there is a good reason. It's not important that event
                     // thumbnails have alt text, so we don't record errors for those either.