Updates to Slack connector to support file upload

Available on Retool Cloud and in self-hosted Retool 3.168 or later.

Retool's Slack integration now supports the files.getUploadURLExternal and files.completeUploadExternal APIs for uploading files. Slack ended support for their files.upload API on March 11, 2025, and this endpoint is no longer available in the Retool Slack integration.

For most users, no action is required to access the new APIs. For self-hosted organizations that set the SERVE_LOCAL_SPECS environment variable, you must upgrade to version 3.168.0-edge, patch release 3.148.2, or patch release 3.114.17 to access this change.

The workaround described in the Action Required: Update Slack queries using files.upload changelog entry is no longer required.