SASL frontend mechanisms are implemented with pg_fe_sasl_mech and
not the _be_ variant which is the backend implementation. Spotted
while reading adjacent code.
/*
* Frontend SASL mechanism callbacks.
*
- * To implement a frontend mechanism, declare a pg_be_sasl_mech struct with
+ * To implement a frontend mechanism, declare a pg_fe_sasl_mech struct with
* appropriate callback implementations, then hook it into conn->sasl during
* pg_SASL_init()'s mechanism negotiation.
*/