true, each future attempt to save the message metadata or
data will use a high durability write, delaying further processing until the
message data has been written to the spool.
false, which is the default setting, whether high durability
writes are used is a function of the configuration of the spool(s) that you
have enabled in your configuration.
Using this together with RocksDB spool can be incredibly harmful to overall performance, as forcing a flush is a database-wide operation.