Password Migration from Grails 2 to Grails 4. (Spring-security 3 to Spring-security 5)

Disclaimer : This is my first post. You have to bear it. ;D

I want to jump in straight. I was going through an upgrade of a backend system which was on grails version 2.5.1 and we wanted to upgrade to the latest grails version. I picked up version 4.0.3.

Grails plugin being used for spring-security-core for grails 2.5.1 is spring-security-core:2.0-RC6 which uses spring-security-core-3.2.9 (in spring perspective). The new app : Grails 4.0.2 uses spring-security-core:4.0.2 which in turn uses spring-security-core:5.1.8 .
So now we are using Spring-security 5.

I started upgrading the app by migrating the database at first and…