Support for External Credentials Provider

[dustindclark]

This is a feature request. Looking for a clean way to inject an external credentials provider so that I don't have to store plain text credentials in SCM, environment variables, JVM startup params, etc. This is the only workaround that I've found, and obviously it's not a good one:

@CompileStatic
class BootStrap {
    SecretManagerService secretManagerService
    MailSender mailSender

    def init = { servletContext ->
        final Secret secret = secretManagerService.getSecret('my-secret-name')
        setMailPassword(secret)
    }

    @CompileDynamic
    void setMailPassword(final Secret secret) {
        //TODO: this is really bad.
        mailSender.username = secret.username
        mailSender.password = secret.password
    }
}

Obviously the default implmentation should remain as-is and use config, but I would like to inject my credential manager accordingly. Thanks!