This issue covers the severity icon displayed in instant email bodies, next to the title.

Acceptance criteria:

• When an event is submitted to Notifications through Kafka or the Notifications gateway (test both if possible) with a known severity, the corresponding icon is displayed next to the title.
• When an event is submitted to Notifications through Kafka or the Notifications gateway (test both if possible) with no severity, the event is not rejected and no icon is displayed next to the title.
• When an event is submitted to Notifications through Kafka or the Notifications gateway (test both if possible) with an unknown severity, the event is not rejected and no icon is displayed next to the title.