Investigate default Severity field

[grahamalama]

JBI specifies a default field id for users who want to sync Severity.

Twice now (1, 2), we've had to override that default field to a different one.

We should:

• investigate whether customfield_10319 should be the new default
• somehow include in the heartbeat check that if a project specifies syncing severity, the specified field is available on the screens where it's needed
• (anything else?)

[leplatrem]

somehow include in the heartbeat check that if a project specifies syncing severity, the specified field is available on the screens where it's needed

This requires admin permission unfortunately