The current qualified validator election sets two conditions
1. has the desire to win the election.
2. meets the threshold of a valid candidate.
Even if the candidate satisfies the above 2 conditions, the candidate will be discarded by Session module,
because the session keys are not set (call pallet-session::set_keys) (without any prompt log message).
To avoid this low-level error, we add a third condition
3. has set session keys by calling pallet_session set_keys.
Determine whether this candidate has set session keys by the trait ValidatorRegistration,
The current qualified validator election sets two conditions
Even if the candidate satisfies the above 2 conditions, the candidate will be discarded by
Sessionmodule, because the session keys are not set (call pallet-session::set_keys) (without any prompt log message).To avoid this low-level error, we add a third condition
Determine whether this candidate has set session keys by the trait
ValidatorRegistration,