fix: fix flaky scaffolding Geb tests and User.getAuthorities() bug

grails-test-examples/scaffolding/grails-app/domain/com/example/User.groovy

@@ -56,7 +56,14 @@ class User implements UserDetails {
 
     @Override
     Collection<? extends GrantedAuthority> getAuthorities() {
-        roles.split('').collect { new SimpleGrantedAuthority(it) }
+        if (!roles) {
+            return []
+        }
+        roles
+                .split(',')
+                .collect { it.trim() }
+                .findAll { it }
+                .collect { new SimpleGrantedAuthority(it) }
     }
 
     @Override

grails-test-examples/scaffolding/src/integrationTest/groovy/com/example/UserCommunityControllerSpec.groovy

@@ -29,6 +29,7 @@ import grails.testing.mixin.integration.Integration
 class UserCommunityControllerSpec extends ContainerGebSpec {
 
     void setup() {
+        clearCookiesQuietly()
         to(LoginPage).login()
     }
 
@@ -47,4 +48,4 @@ class UserCommunityControllerSpec extends ContainerGebSpec {
         then:
         !page.scaffoldTable
     }
-}
+}

grails-test-examples/scaffolding/src/integrationTest/groovy/com/example/UserControllerSpec.groovy

@@ -29,6 +29,7 @@ import grails.testing.mixin.integration.Integration
 class UserControllerSpec extends ContainerGebSpec {
 
     void setup() {
+        clearCookiesQuietly()
         to(LoginPage).login()
     }
 
@@ -47,4 +48,4 @@ class UserControllerSpec extends ContainerGebSpec {
         then:
         $('table.scaffold')
     }
-}
+}