CKEditor 5 Plugin

You are a senior CKEditor 5 plugin architect. I need you to build a complete CKEditor 5 plugin called "NewsletterPlugin". Context: - This is a migration from a legacy CKEditor 4 plugin. - Must follow CKEditor 5 architecture strictly. - Must use CKEditor 5 UI framework and plugin system. - Must follow documentation: https://ckeditor.com/docs/ckeditor5/latest/framework/architecture/ui-components.html https://ckeditor.com/docs/ckeditor5/latest/features/html/general-html-support.html Environment: - CKEditor 5 custom build - ES6 modules - Typescript preferred (if possible) - No usage of CKEditor 4 APIs ======================================== FEATURE REQUIREMENTS ======================================== 1) Toolbar Button: - Add a toolbar button named "newsletter" - Icon: simple SVG placeholder - When clicked → open a dialog (modal) 2) Dialog Behavior: The dialog must contain input fields: - title (text input) - description (textarea) - tabs (dynamic list, user can add/remove tab items) Each tab item: - tabTitle - tabContent (HTML allowed) Buttons: - Cancel - OK 3) On OK: - Generate structured HTML block inside editor - Structure example: <div class="newsletter"> <ul class="newsletter-tabs"> <li class="active"> <a href="#tab-1" class="active">Tab 1</a> </li> <li> <a href="#tab-2">Tab 2</a> </li> </ul> <div class="newsletter-content"> <div id="tab-1" class="tab-pane active"> Content 1 </div> <div id="tab-2" class="tab-pane"> Content 2 </div> </div> </div> 4) Behavior inside editor: - First tab always active by default. - When user clicks <a> tab link: - Remove class "active" from all tabs and panes - Add class "active" to clicked tab and corresponding pane - When user double-clicks <a>: - Open dialog again - Load existing data - Allow editing - Update HTML structure 5) MUST USE: - GeneralHtmlSupport (GHS) for allowing custom classes & attributes - Proper upcast / downcast converters - Widget API (toWidget, toWidgetEditable if needed) - Command class - UI Component system (ButtonView, View, InputTextView) - Editing & UI part separated - Schema registration properly 6) Architecture required: Create structure: - newsletter/ - newsletterplugin.ts - newsletterediting.ts - newsletterui.ts - newslettercommand.ts 7) Technical requirements: - Register schema element: newsletterBlock - Must allow: class id href data attributes - Use: editor.model.change() conversion.for('upcast') conversion.for('downcast') - Handle click event via editing view document - Use editing.view.document.on( 'click', ... ) - Detect double click event 8) Important: Do NOT use raw DOM manipulation. All updates must go through editor.model. 9) Output required: - Full plugin code - Proper imports - Comments explaining architecture - Explain migration differences from CKEditor 4 - Show how to register plugin in build 10) Extra: Explain how to enable GeneralHtmlSupport configuration in editor config. ======================================== Please produce clean production-ready code. Do not simplify logic. Follow CKEditor 5 best practices strictly.