Alert description parsing

[eric-gade]

What does this PR do? 🛠️

Per #589, this PR implements basic Alert description field parsing, along with basic integration into the alert template.

What does the reviewer need to know? 🤔

The parsing is regex based. It will look for any word in all caps followed by ellipses, and use that as the label. This means we don't specifically search for WHAT/WHEN/WHERE/IMPACTS tokens. If we want to be more literal to the observed format, and more strict, we can switch over.

When the regex matches successfully, the description field on the processed alert object will become an associative array whose keys are the labels in lowercase ("what" "where" etc) and whose values are the text content for that label.

When the regex fails to match, the plain description string is displayed, with the white space adjusted.

Screenshots (if appropriate): 📸

Before:

After:

[eric-gade]

There is no good way in a twig template to determine if some attribute on an object in question is or is not an array. Here the alert.description field will be an array with named keys. Otherwise it's just the description string itself. We use this boolean field in the twig template to determine how we display the field.

[greg-does-weather]

I haven't pulled this down and run it locally yet, but the code looks good!

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