Party Bus reported an issue where the AuthorizationPolicy being generated by bb-common for their `custom` gateway was not aligning with the actual service account name being deployed. This was due to the fact that currently we specify an explicit service account name in the defaults for two default gateways (public and passthrough) - https://repo1.dso.mil/big-bang/bigbang/-/blob/master/chart/templates/istio-gateway/_defaults.tpl?ref_type=heads#L27 which aligns with how [bb-common's automatic AuthorizationPolicy generation works](https://repo1.dso.mil/big-bang/product/packages/bb-common/-/blob/main/chart/templates/routes/inbound/_authz.tpl?ref_type=heads#L32). Naively, I would have expected us to just use the default service account names which would alleviate any additional effort for custom gateways.