New site setting to enable or disable rich text pasting

app/assets/javascripts/discourse/components/composer-editor.js.es6

@@ -434,9 +434,14 @@ export default Ember.Component.extend({
     });
 
     $element.on('fileuploadpaste', (e) => {
-      const { types } = clipboardData(e);
       this._pasted = true;
 
+      if (!this.siteSettings.enable_rich_text_paste || !$(".d-editor-input").is(":focus")) {
+        return;
+      }
+
+      const { types } = clipboardData(e);
+
       if (types.includes("text/plain") || types.includes("text/html")) {
         e.preventDefault();
       }

app/assets/javascripts/discourse/components/d-editor.js.es6

@@ -640,7 +640,7 @@ export default Ember.Component.extend({
   },
 
   paste(e) {
-    if (!$(".d-editor-input").is(":focus")) {
+    if (!this.siteSettings.enable_rich_text_paste || !$(".d-editor-input").is(":focus")) {
       return;
     }
 

config/locales/server.en.yml

@@ -1088,6 +1088,7 @@ en:
     top_page_default_timeframe: "Default timeframe for the top view page."
     show_email_on_profile: "Show a user's email on their profile (only visible to themselves and staff)"
     prioritize_username_in_ux: "Show username first on user page, user card and posts (when disabled name is shown first)"
+    enable_rich_text_paste: "Enable automatic HTML to Markdown conversion"
 
     email_token_valid_hours: "Forgot password / activate account tokens are valid for (n) hours."
 

config/site_settings.yml

@@ -525,6 +525,9 @@ posting:
   enable_markdown_typographer:
     client: true
     default: true
+  enable_rich_text_paste:
+    client: true
+    default: false
   suppress_reply_directly_below:
     client: true
     default: true