move extensions-api to libs

src/Umbraco.Web.UI.Client/libs/extensions-api/create-extension-element.function.ts

@@ -0,0 +1,31 @@
+import type { ManifestElement } from '../models';
+import { hasDefaultExport } from './has-default-export.function';
+import { isManifestElementNameType } from './is-manifest-element-name-type.function';
+import { loadExtension } from './load-extension.function';
+
+export async function createExtensionElement(manifest: ManifestElement): Promise<HTMLElement | undefined> {
+	
+	//TODO: Write tests for these extension options:
+	const js = await loadExtension(manifest);
+
+	if (isManifestElementNameType(manifest)) {
+		// created by manifest method providing HTMLElement
+		return document.createElement(manifest.elementName);
+	}
+
+	// TODO: Do we need this except for the default() loader?
+	if (js) {
+		if (hasDefaultExport(js)) {
+			// created by default class
+			return new js.default();
+		}
+
+		console.error('-- Extension did not succeed creating an element, missing a default export of the served JavaScript file', manifest);
+
+		// If some JS was loaded and it did not at least contain a default export, then we are safe to assume that it executed as a module and does not need to be returned
+		return undefined;
+	}
+
+	console.error('-- Extension did not succeed creating an element, missing a default export or `elementName` in the manifest.', manifest);
+	return undefined;
+}