Mailer: default mailer beans are not registered if only mail template record is used

[mkouba]

Describe the bug

This use case is described in the docs:

import io.quarkus.mailer.MailTemplate;
import io.quarkus.qute.CheckedTemplate;

@Path("")
public class MailingResource {

    record hello(String name) implements MailTemplateInstance { 
    }

    @GET
    @Path("/mail")
    public Uni<Void> send() {
        // the template looks like: Hello {name}! 
        return new hello("John")
           .to("[email protected]")  
           .subject("Hello from Qute template")
           .send(); 
    }
}

We should fix the condition here: https://github.com/quarkusio/quarkus/blob/main/extensions/mailer/deployment/src/main/java/io/quarkus/mailer/deployment/MailerProcessor.java#L104-L108

Expected behavior

No response

Actual behavior

Application fails with NPE.

How to Reproduce?

No response

Output of uname -a or ver

No response

Output of java -version

No response

Quarkus version or git rev

No response

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response

[quarkus-bot]

/cc @cescoffier (mailer)