Updating to Grails 6.1.1

[jdaugherty]

Updating to Grails 6.1.1.

[jdaugherty]

@jamesfredley this was my initial pass at merging my changes to support grails 6. Once we have an initial review done, I'll iterate on the build actions to get them working end-to-end.

[jdaugherty]

Per discussion, the testapp-profile was used as part of the old travis CI testing. It looks like the test run there used to:

1. Build the project & install into local maven
2. Use grails profile to generate various test apps

Other than generating the grails apps, I can't see where those apps were ever used. I assume they were used for manual testing. It also looks like past github CI's only ever ran gradle check and published all of the gradle projects except spring-security-rest-testapp-profile.

Running gradle build at the root will treat the testapp-profile as a grails project - likely because grails-shell was originally removed in later versions of grails. This build will fail due to the same reason grails/grails-gradle-plugin#316 was created. For now, I'm going to remove the gradle project spring-security-rest-testapp-profile since we haven't tested with it since 2020 and because there are old secrets for APIs that aren't even valid anymore.

We can always restore this subproject later if we get profiles working correctly.