[Slack integration] files.completeUploadExternal.initial_comment does not support mrkdwn format

[teka23]

actions/src/actions/slack/utils.ts

Line 143 in f9a87a9

initial_comment: request.formParams.initial_comment ? request.formParams.initial_comment : "",

It looks like files.completeUploadExternal.initial_comment does not support mrkdwn format and the comment is showing up as plain text.

[teka23]

slackapi/node-slack-sdk#1561

[teka23]

As Slack people recommended, we might need to upload the file first and use that file as an attachment.
Or, send comment first and add the attachment to the thread