[Notifications] Fix Slack Notifications With Long Messages (#5489)

* fix slack notifications with long messages

* better

* like this

---------

Co-authored-by: quaark <a.melnick@icloud.com>

mlrun/utils/notifications/notification/slack.py

@@ -72,12 +72,7 @@ def _generate_slack_data(
         event_data: mlrun.common.schemas.Event = None,
     ) -> dict:
         data = {
-            "blocks": [
-                {
-                    "type": "header",
-                    "text": {"type": "plain_text", "text": f"[{severity}] {message}"},
-                },
-            ]
+            "blocks": self._generate_slack_header_blocks(severity, message),
         }
         if self.name:
             data["blocks"].append(
@@ -106,6 +101,32 @@ def _generate_slack_data(
 
         return data
 
+    def _generate_slack_header_blocks(self, severity: str, message: str):
+        header_text = block_text = f"[{severity}] {message}"
+        section_text = None
+
+        # Slack doesn't allow headers to be longer than 150 characters
+        # If there's a comma in the message, split the message at the comma
+        # Otherwise, split the message at 150 characters
+        if len(block_text) > 150:
+            if ", " in block_text and block_text.index(", ") < 149:
+                header_text = block_text.split(",")[0]
+                section_text = block_text[len(header_text) + 2 :]
+            else:
+                header_text = block_text[:150]
+                section_text = block_text[150:]
+        blocks = [
+            {"type": "header", "text": {"type": "plain_text", "text": header_text}}
+        ]
+        if section_text:
+            blocks.append(
+                {
+                    "type": "section",
+                    "text": self._get_slack_row(section_text),
+                }
+            )
+        return blocks
+
     def _get_alert_fields(
         self,
         alert: mlrun.common.schemas.AlertConfig,