broker: prevent panic by checking for nil on channel close

amqp broker: do not attempt to create a channel if no connection is a…

…live

extend (wrongly used) interface to allow injecting interceptors

extend (wrongly used) interface to allow injecting interceptors

adapt interceptors to new metadata key

Signed-off-by: lukas <[email protected]>

add internal metadata key

Signed-off-by: lukas <[email protected]>

fix wrong connection use for publishing; add name to connection for b…

…etter logging

Signed-off-by: lukas <[email protected]>

add NewClientWithAddress to grpc client

Signed-off-by: lukas <[email protected]>

minor changes to publish connection pooling; log fixes

Signed-off-by: lukas <[email protected]>

improve grpc logging

Signed-off-by: lukas <[email protected]>