Add validation annotations to CleanupConfig

[sleberknight]

Add Jakarta Bean Validation annotations to the CleanupConfig class to permit validation, for example if an application uses external configuration to specify the configuration to use when cleaning up application errors.

This does not require adding a new dependency, since this library already depends (transitively) on jakarta.validation:jakarta.validation-api. However, it does now make it an explicit dependency, so we should probably make it explicit in the POM.

[sleberknight]

Since we're using Dropwizard's Duration class (io.dropwizard.util.Duration) in this configuration class, it makes sense to not only use standard validation Jakarta Bean Validation annotations like @NotNull but also to use Dropwizard's own custom validation annotations, in this case to use @MinDuration on the Duration fields. Since we mainly want to ensure that the duration isn't zero (or even negative), we can make the minimum as 1 minute for the fields. That probably isn't very useful in real life for most applications, but it ensures there is at least a valid minimum. I don't think we should set any maximum durations, since maybe someone wants to save them for 1 year, 2 years, etc. or even effectively forever by using a very large number of days.

So, we'll also want to add dropwizard-validation as an explicit dependency. Currently it is a transitive dependency via dropwizard-core.