Previously, up to 3 calls to SetUserQuota() could be made. This has been
consolidated into a single call. Additionally, the `addtionalConfigSpec`
struct is introduced to centralize handling of `.spec.additionalConfig`
keys and as foundational work to support new keys in the future.
Signed-off-by: Joshua Hoblitt <josh@hoblitt.com>
(cherry picked from commit 9243764359)