Allow users to modify the messages of Slack notifications

At the current moment, when integrated with Bitbucket Cloud, the Slack notifications can be too simple such as just mentioning the branch name or informing that “someone” approved your pull request etc.

It would be great if the message body can be configured to be more verbose and provided more detailed information such as the repository name etc.

Otherwise, it would also be great if users are able to create templates for these Slack notifications, allowing them to use custom messages.