Refresh brokers given list of seed brokers

[justin-chen]

RefreshBrokers takes a list of addresses to be used as seed brokers.
Existing broker connections are closed and the updated list of seed brokers will be used for the next metadata fetch.

RefreshBrokers can be used in the case of failovers when the Kafka cluster's DNS would have to be re-resolved

[vvuibert]

LGTM

[d1egoaz]

I'm not sure how Sarama folks are adding new features, but this looks like it's a breaking change if someone is implementing the interface 🤔

not sure why someone would do that, but the interface is public 🤷

we could add a trick that I saw in the golang code, to add a private method, so no apps could implement the interface

    // A private method to prevent users implementing the
    // interface and so future additions to it will not
    // violate Go 1 compatibility.
    private()

found the blog post: https://blog.golang.org/module-compatibility

[justin-chen]

Good idea, i'll add a dummy private() method to the interface in another PR

[justin-chen]

#1785

[d1egoaz]

😞 this wasn't a good idea at the end :/ the initial intention of private() is if the user needs to use an interface but don't want other people to implement it, and this is not the case for this interface.