The docs do say which GUCs can be changed only by superusers, but we
forgot to mention this for the new log_transaction_sample_rate. This
GUC was introduced in PostgreSQL 12, so backpatch accordingly.
Author: Adrien Nayrat
Backpatch-through: 12
logs all statements for all transactions.
log_transaction_sample_rate is helpful to track a
sample of transaction.
+ Only superusers can change this setting.