[FEATURE] Customise email notifications title

[IndWalker]

Tell us about the problem you're trying to solve
Notifications email title is not customisable and dependent solely on the notification timestamp.

I'm trying to include some additional metadata to email notifications title to better categorise them based on environments for which re_data is running.

Describe the solution you’d like

Add additional parameter to re_data notify email CLI command --title <CUSTOM_TITLE> and format title with it when message is built.

Describe the alternative you’ve considered or used

Creating different senders for different environments and then categorise email by senders, but it looks like an overhead for my kind of problem.

[FrankTub]

In addition to this ticket I think it would be really benificial to be able to customize what is sent in a notification. For example a description about what it means that a specific test failed or some example data along with the notification to solve the data issue.