Host header initialization breaking change in StompRelayMessageBrokerHandler #36907

This is related to #36663 / #36673 (comment)

There I wrote:

I don't know if this also lead to problem like mine in other cases: Due to this change, the client could not connect to the external broker (RabbitMQ in my case) and responded with error Virtual host 'localhost' access denied.

RabbitMQ has a standard virtual host configured with name '/'. The RabbitMQ STOMP docs says that if there is no host set in the headers it defaults to '/'.

In order to fix this error I have to set the virtual host in the StompBrokerRelayRegistration explicitly to '/'.

In my eyes this change is a breaking change and should have been mentioned somewhere.