Add Microsoft Teams notification functionality

[christosku]

• Add the ability to send health notifications to a Microsoft Teams webhook using Microsoft Teams Notification Channel
• Rename health::notifications.check_failed_slack_message to health::notifications.check_failed_notification_message in order to reuse it for both Slack and Teams
• Add documentation for this feature

[freekmurze]

Thanks you for this! Although it is nicely implemented, we're going to pass on this as we don't need this integration ourselves. In your project you can use a custom notification where you can add the Microsoft teams functionality.

[christosku]

You are welcome! I will follow your suggestion :)