docs: Change wrong info about controller default scope

[matrei]

No description provided.

[puneetbehl]

There used to be a default configuration to set the default scope for controller as Singleton. If this is not the case this is a bug. I have noticed that somewhere we have accidentally removed the following from the application.yml in Grails 6.

grails
    controllers:
        defaultScope: singleton

[matrei]

@puneetbehl Yes, the missing configuration is also an issue: grails/grails-forge#263. But changing the default scope in configuration does not make it the default scope of the framework. The default scope of controllers in Grails is prototype unless changed in config. The docs says different things in different places: https://docs.grails.org/6.1.1/guide/single.html#_scoped_controllers, https://docs.grails.org/6.1.1/ref/Controllers/scope.html. I also think that the default controller scope should eventually be changed, as proposed by grails/grails-core#13332.

[puneetbehl]

The default scope in the framework is configured to prototype. For newly created application it overridden by the above mentioned configuration. The idea behind it was to change the default scope to singleton in next major Grails version and remove it from the configuration which is clearly missed. I think we should merge grails/grails-core#13332 and update the documentation to reflect singleton as the default scope.

[matrei]

Yes, I agree! But for Grails 6.1.x the documentation is wrong and this PR addresses that.

[puneetbehl]

The documentation will only be released with the next patch or minor release where we will change the default to singleton as this is a bug and the change was not intentional. So, I think we should keep the singleton as the default option and fix the problem in Grails Core.

The docs says different things in different places:

We should address it in this PR.

[matrei]

I think we need to separate the issues in grails-forge and grails-core.

The bugfix in grails-forge should be applied to both 6.0.x and 6.1.x where the default controller scope is still prototype.

We should not change default controller scope in grails-core 6.1.x or earlier as that would change behavior in a patch release.
In grails-core 6.2.x it could be changed and there also change the documentation about this.

After the behavior has been updated in grails-core 6.2.x the configuration can be removed in grails-forge 6.2.x as it will then be superfluous.

However, this PR is regarding behavior in grails-core 6.1.x where the default controller scope is still prototype and the documentation says it is singleton.