Slack webhook transport.

Sends messages to Slack channels via webhooks (async via Oban).

Configuration

Requires webhook_url in channel metadata or via callback:

# Inline configuration
event :order_created,
  channels: [
    [
      transport: :slack,
      audience: :team,
      metadata: [
        webhook_url: "https://hooks.slack.com/services/..."
      ]
    ]
  ]

# Or via callback module
def channels(context) do
  [
    %Channel{
      transport: :slack,
      audience: :team,
      metadata: %{
        webhook_url: get_slack_webhook_url(:orders)
      }
    }
  ]
end

Content

Slack messages support:

• notification_message - Simple text content (supports Slack mrkdwn)
• slack_blocks - Block Kit layout blocks for rich formatting
• slack_attachments - Legacy attachment format
• slack_username - Override bot username
• slack_icon_emoji - Override bot icon with emoji
• slack_icon_url - Override bot icon with image URL

Example with blocks:

content: [
  notification_message: "New order received!",
  slack_blocks: [
    %{
      type: "header",
      text: %{type: "plain_text", text: "Order {{id}} Created"}
    },
    %{
      type: "section",
      fields: [
        %{type: "mrkdwn", text: "*Customer:*\n{{user.name}}"},
        %{type: "mrkdwn", text: "*Total:*\n${{total}}"}
      ]
    }
  ]
]

Slack Message Formatting

Slack uses mrkdwn (markdown-like) formatting:

• *bold* - Bold text
• _italic_ - Italic text
• ~strikethrough~ - Strikethrough
• `code` - Inline code
• code block - Code block
• <url|text> - Hyperlink