Add Inbox Note example code to docs (https://github.com/woocommerce/woocommerce-admin/pull/8019)

* Add Inbox Note example extension

* Typo

* Put into class

* Fix premature class import, moved note check logic to its own method

plugins/woocommerce-admin/docs/examples/extensions/simple-inbox-note/class-simpleinboxnote.php

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+<?php
+/**
+ * WooCommerce Admin SimpleInboxNote example class.
+ *
+ * Adds an example note to the merchant's inbox.
+ *
+ * @package WooCommerce\Admin
+ */
+
+use Automattic\WooCommerce\Admin\Notes\Note;
+use Automattic\WooCommerce\Admin\Notes\NoteTraits;
+
+/**
+ * SimpleInboxNote class.
+ */
+class SimpleInboxNote {
+	/**
+	 * Note traits.
+	 */
+	use NoteTraits;
+
+	/**
+	 * Name of the note for use in the database.
+	 */
+	const NOTE_NAME = 'simple-inbox-note';
+
+	/**
+	 * Check to run to find out if we should display our note.
+	 *
+	 * @return Note
+	 */
+	public static function is_applicable() {
+		// We want to show the note after five days.
+		if ( ! self::is_wc_admin_active_in_date_range( 'week-1-4', 5 * DAY_IN_SECONDS ) ) {
+			return false;
+		}
+		return true;
+	}
+
+	/**
+	 * Get the note.
+	 *
+	 * @return Note
+	 */
+	public static function get_note() {
+		// Optionally, you can add any logic here in order to
+		// control when the note should be displayed.
+		// In the future, this would be automatically handled by our NoteTraits.
+		// if ( ! self::is_applicable() ) {
+		// return;
+		// } //.
+
+		// Instantiate a new Note object.
+		$note = new Note();
+
+		// Set our note's title.
+		$note->set_title( 'Hello From Inbox Note!' );
+
+		// Set our note's content. Please keep in mind that the note content
+		// is limited to 320 displayable characters.
+		// It is also not advisable to include Unicode characters such as emojis
+		// since they could possibly not work on some user's sites where database
+		// collation doesn't support Unicode.
+		$note->set_content(
+			sprintf(
+				'This is your note example contents. You may enter up to 320 displayable characters here. For more information on character limit, visit our <a href="https://developer.woocommerce.com/2021/11/10/introducing-a-320-character-limit-to-inbox-notes/">blogpost</a>.'
+			)
+		);
+
+		// In addition to content, notes also support structured content.
+		// You can use this property to re-localize notes on the fly, but
+		// that is just one use. You can store other data here too. This
+		// is backed by a longtext column in the database.
+		$note->set_content_data(
+			(object) array(
+				'getting_started' => true,
+			)
+		);
+
+		// Set the type of the note. Note types are defined as enum-style
+		// constants in the Note class. Available note types are:
+		// error, warning, update, info, marketing.
+		$note->set_type( Note::E_WC_ADMIN_NOTE_INFORMATIONAL );
+
+		// Set the type of layout the note uses. Supported layout types are:
+		// 'banner', 'plain', 'thumbnail'.
+		$note->set_layout( 'plain' );
+
+		// Set the image for the note. This property renders as the src
+		// attribute for an img tag, so use a string here.
+		$note->set_image( '' );
+
+		// Set the note name and source. You should store your extension's
+		// name (slug) in the source property of the note. You can use
+		// the name property of the note to support multiple sub-types of
+		// notes. This also gives you a handy way of namespacing your notes.
+		$note->set_source( 'simple-inbox-note-example' );
+		$note->set_name( self::NOTE_NAME );
+
+		// Add action buttons to the note. A note can support 0, 1, or 2 actions.
+		// The first parameter is the action name, which can be used for event handling.
+		// The second parameter renders as the label for the button.
+		// The third parameter is an optional URL for actions that require navigation.
+		$note->add_action(
+			'settings',
+			'Open Settings',
+			'?page=wc-settings&tab=general'
+		);
+
+		// Return the note object.
+		return $note;
+	}
+}

plugins/woocommerce-admin/docs/examples/extensions/simple-inbox-note/woocommerce-admin-simple-inbox-note-example.php

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+<?php
+/**
+ * Plugin Name: WooCommerce Admin Simple Inbox Note Example
+ *
+ * @package WooCommerce\Admin
+ */
+
+/**
+ * Add note.
+ */
+function add_note() {
+	require_once dirname( __FILE__ ) . '/class-simpleinboxnote.php';
+	SimpleInboxNote::possibly_add_note();
+}
+
+/**
+ * Delete note.
+ */
+function delete_note() {
+	require_once dirname( __FILE__ ) . '/class-simpleinboxnote.php';
+	SimpleInboxNote::possibly_delete_note();
+}
+
+// Attempt to add the note on plugin activation.
+add_action( 'activated_plugin', 'add_note' );
+
+// Delete the note when plugin is deactivated.
+add_action( 'deactivated_plugin', 'delete_note' );