Formatting the test_results_sample as a table within the Slack alerts

[gautierdp]

Is your feature request related to a problem? Please describe.
When generating the Slack Alerts, currently the test_results_sample returns a JSON object. It would be much nicer to have this formatted as a table.

Describe the solution you'd like
The test_results_sample is formatted like a table.

Additional context
This is a feature that would be greatly appreciated by the consumers of these slack alerts who are not always technically inclined.

[gofford]

This is a big sticking point for our adoption of Elementary as a general alerting tool. Many of the people who will consume the alerts are not technical, and not familiar with JSON.

Being able to render the the results as a nicely formatted Markdown table would greatly enhance usability for our internal teams.

[gofford]

This is quite an old issue but one that comes up time and time again when we are trying to use elementary as a way to notify non-technical people of issues with data.

Is this likely to ever happen?