Exchange name convention for direct routing topology is incorrectly typed

[adamralph]

The only time the user specified exchange name convention is invoked, it is passed null for both the address and eventType parameters -

NServiceBus.RabbitMQ/src/NServiceBus.RabbitMQ/Routing/DirectRoutingTopology.cs

Line 48 in fc98f52

string ExchangeName() => conventions.ExchangeName(null, null);

The proposed solution is to either remove the exchange name convention parameter, or make it a string -

NServiceBus.RabbitMQ/src/NServiceBus.RabbitMQ/Configuration/RabbitMQTransportSettingsExtensions.cs

Line 19 in fc98f52

public static TransportExtensions<RabbitMQTransport> UseDirectRoutingTopology(this TransportExtensions<RabbitMQTransport> transportExtensions, Func<Type, string> routingKeyConvention = null, Func<string, Type, string> exchangeNameConvention = null)

Plan of attack

• Make change - fix exchange name convention parameter #420
• Update docs, including the upgrade guide - Rabbit updates for v5 changes docs.particular.net#3256

[adamralph]

@Particular/rabbitmq-transport-maintainers discussed this today. The solution we will go with is changing the parameter to type Func<string>, since it is not possible to pass the address and eventType at the time of the delegate invocation.