This is one of the original RFEs from OCM that led to the creation of RHCLOUD-37873. We can generalize it to all tenants though, to be confirmed by our PM.

Acceptance criteria:

• Templates from the engine module MUST NOT be updated.
• Use the beta email template feature for all changes done from this ticket. Ask glepage@redhat.com or rh-ee-gduval for guidance if needed.
• Add the severity as an optional first value to the OCM instant email subject. Update the OCM template unit tests accordingly.
• After both this ticket and RHCLOUD-41539 are done, submit an updated instant email subject and body to the OCM PM and ask for their validation.
• To be confirmed by our PM: add the severity as an optional first value to the default instant email subject. This would impact the email subject from all tenants besides OCM. Update all unit tests accordingly.
• Check the templates dedicated to special environments and update them as well.