Return sensible HTTP status code such as "503" during backup instead of "500" or 302 redirect to errorEvents.action

Problem Definition

When Bamboo is down for maintenance during a backup / export, calls to the Bamboo web server return an HTTP status code of 500 or 302 redirect to errorEvents.action, which is defined as "Internal Server Error: A generic error message, given when an unexpected condition was encountered and no more specific message is suitable." (from Wikipedia)
This may present issues for customers looking to monitor their applications by HTTP status code, as a 500 response could be indicative of a number of different issues and can't necessarily be considered a "working" response.

Suggested Solution

Bamboo should instead return 503, defined as "Service Unavailable: The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state." This would provide a more specific and accurate HTTP response.

REST endpoints to return the server status such as rest/api/latest/server, should be exempt from the 302 redirect and return the server state as part of the response aka state:MAITENANCE

Workaround

N/A