Add function to send files to Slack channels

We want to be able to upload logs as text files to specified channels. Add a function to the Slack utils module that will accept the file details and upload it to Slack.

assigned to @james413

created branch 44-add-function-to-send-files-to-slack-channels to address this issue

mentioned in merge request !59 (merged)

mentioned in commit 0a7b47c9

Released to main