Problem

The message step currently sends plain text to Slack using plain_text block type, which means Slack mrkdwn formatting syntax (bold, italic, links, code) is rendered literally instead of being formatted.

Example of current behavior:

step "message" "alert" {
    notifier = notifier.slack_ops
    text     = "*Alert*: Check <https://console.aws.amazon.com|AWS Console>"
}

What Slack shows: *Alert*: Check <https://console.aws.amazon.com|AWS Console> (literal characters)

What users expect: Alert: Check AWS Console (formatted)

Use Case

Users who rely on notifiers (e.g., having read-only Slack access but using a shared notifier with write permissions) cannot send formatted messages. This is particularly important for:

• Security alerts that need visual emphasis
• Notifications with clickable links
• Status updates with structured formatting

Proposed Solution

Add an optional mrkdwn boolean parameter to the message step:

step "message" "alert" {
    notifier = notifier.slack_ops
    text     = "*Alert*: Check <https://console.aws.amazon.com|AWS Console>"
    mrkdwn   = true  # NEW - enables Slack mrkdwn formatting
}

When mrkdwn = true, the message step uses mrkdwn type instead of plain_text in the Block Kit payload.

Technical Details

The root cause is in internal/primitive/message.go:

// CURRENT
promptBlock := slack.NewTextBlockObject(slack.PlainTextType, icm.Text, false, false)

// PROPOSED
textType := slack.PlainTextType
if icm.Mrkdwn {
    textType = slack.MarkdownType
}
promptBlock := slack.NewTextBlockObject(textType, icm.Text, false, false)

Backward Compatibility

• Default: mrkdwn defaults to false (unset)
• Existing pipelines work exactly as before
• New pipelines can opt-in to formatting

Platform Note

Testing revealed that Slack's mobile app partially renders formatting in plain_text blocks (bold, italic, code) but not links. Desktop shows everything as literal characters. Using mrkdwn=true ensures consistent rendering across all Slack clients.