add credentials in conf.yaml.example

[luisfroliveira]

add the fields rabbitmq_user and rabbitmq_pass so that the agent can authenticate to the rabbitmq api

What does this PR do?

It is necessary to add the fields rabbitmq_user and rabbitmq_pass so that the agent can authenticate to the rabbitmq api

Motivation

errors when trying to integrate datadog into rabbitmq with management plugin

Additional Notes

I also added the service field to the logs

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] Changelog entries must be created for modifications to shipped code
• [ ] Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• [ ] If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[HadhemiDD]

You don't modify the file directly, you should update the spec.yaml and then run the ddev commands to sync: dev validate config --sync <integration> ddev validate models <integration> -s

[ngbrown]

Without this change, the instructions for monitoring host based RabbitMQ don't make sense (https://docs.datadoghq.com/integrations/rabbitmq/?tab=host#rabbitmq-management-plugin5). There is a step to set the password for the datadog user, but no step to use it.