SlackReporter with preformatted rich text

lib/urlwatch/reporters.py

@@ -701,7 +701,7 @@ def submit(self):
 
     def submit_chunk(self, webhook_url, text):
         logger.debug("Sending {} request with text: {}".format(self.__kind__, text))
-        post_data = {"text": text}
+        post_data = self.prepare_post_data(text)
         result = requests.post(webhook_url, json=post_data)
         try:
             if result.status_code == requests.codes.ok:
@@ -715,12 +715,31 @@ def submit_chunk(self, webhook_url, text):
                                                                                         result.content))
         return result
 
+    def prepare_post_data(self, text):
+        return {
+            "blocks": [
+                {
+                    "type": "rich_text",
+                    "elements": [
+                        {
+                            "type": "rich_text_preformatted",
+                            "elements": [
+                                {"type": "text", "text": text}
+                            ]
+                        }
+                    ]
+                }
+            ]
+        }
+
 
 class MattermostReporter(SlackReporter):
     """Send a message to a Mattermost channel"""
 
     __kind__ = 'mattermost'
 
+    def prepare_post_data(self, text):
+        return {"text": text}
 
 class DiscordReporter(TextReporter):
     """Send a message to a Discord channel"""