sessionRegistry get erased upon Grails fast reload

In a Grails 4 webapp with Spring Security plugin dependency

org.grails.plugins:spring-security-core:4.0.0.RC2

in any controller inject dependencies

def springSecurityService
def sessionRegistry

and include this snippet in an action `A`:

println 'principal: ' + springSecurityService.principal?.username
println 'currentUser: ' + springSecurityService.currentUser
println '-------------'
println 'principal sessions: ' + sessionRegistry.getAllSessions(springSecurityService.principal, true)
println 'all principals: ' + sessionRegistry.allPrincipals.collect { it.username }

### Steps to Reproduce

1. run webapp
2. login with valid credentials
3. execute action `A`
4. trigger a fast reload (Spring Dev Tools)
5. execute action `A` again

### Expected Behaviour

Both snippets should print

principal: user@domain.com
currentUser: UserDomainClass(email:user@domain.com)
-------------
principal sessions: [org.springframework.security.core.session.SessionInformation@644c9f8a]
all principals: [user@domain.com]

### Actual Behaviour

2nd execution shows session registry being erased, while principal is maintained as expected

principal: user@domain.com
currentUser: UserDomainClass(email:user@domain.com)
-------------
principal sessions: []
all principals: []

### Environment Information

- **Operating System**: macOS Mojave (10.14.6)
- **GORM Version:** 7.0.0
- **Grails Version (if using Grails):** 4.0.1
- **JDK Version:** 1.8.0_60

Reproduce the issue in a Grails 4.0.1 webapp using spring-security-core 4.0.0.RC2 and Spring Dev Tools, following the listed login and fast-reload steps. Compare sessionRegistry output before and after reload; done means the principal sessions and all principals remain available after the reload.

Written by the indexing model from the issue text.