fix: allow login by email case-insensitive (#7578)

A customer noted that the login by email was case-sensitive, which differs to the handling of the loginname.

This PR changes the email check to be case-insensitive (which it was already in same parts) and improve the search for this as well.

cmd/setup/25.sql

@@ -0,0 +1,2 @@
+ALTER TABLE IF EXISTS projections.users10_notifications ADD COLUMN IF NOT EXISTS verified_email_lower TEXT GENERATED ALWAYS AS (lower(verified_email)) STORED;
+CREATE INDEX IF NOT EXISTS users10_notifications_email_search ON projections.users10_notifications (instance_id, verified_email_lower);