#10158: set HTML document language once per mount/update

As requested, the document language is now set when the component is mounted or the language is changed instead of with every rerender.

web/client/components/I18N/Localized.jsx

@@ -37,7 +37,6 @@ class Localized extends React.Component {
             if (typeof children === 'function') {
                 children = children();
             }
-            document.documentElement.setAttribute("lang", this.props.locale);
 
             return (<IntlProvider key={this.props.locale} locale={this.props.locale}
                 messages={this.flattenMessages(this.props.messages)}
@@ -51,6 +50,22 @@ class Localized extends React.Component {
         return null;
     }
 
+    componentDidMount() {
+        this.updateDocumentLangAttribute();
+    }
+
+    componentDidUpdate(prevProps) {
+        if (this.props.locale !== prevProps.locale) {
+            this.updateDocumentLangAttribute();
+        }
+    }
+
+    updateDocumentLangAttribute() {
+        if (document?.documentElement) {
+            document.documentElement.setAttribute("lang", this.props.locale);
+        }
+    }
+
     flattenMessages = (messages, prefix = '') => {
         return Object.keys(messages).reduce((previous, current) => {
             return typeof messages[current] === 'string' ? {