Send-only endpoint attribute with declarative connection configuration

[andreasohlund]

Replaces startup-registered send-only endpoints with attribute-driven generation and adds declarative connection configuration for both trigger and send-only endpoints.

What changed

• Added [NServiceBusSendOnlyFunction] attribute with optional Connection property to specify the configuration key used to resolve the transport connection
• Added IConnectionSettingManifest interface shared by FunctionManifest and SendOnlyEndpointManifest, providing a uniform ConnectionSettingName property
• Made AzureServiceBusServerlessTransport.ConnectionName internal so that connection configuration only flows through the attribute and source generator pipeline
• Added dedicated SendOnlyEndpointGenerator that discovers and generates registration code for send-only endpoints
• Removed AddSendOnlyNServiceBusEndpoint(...) in favor of generated registrations
• Updated composition generation so builder.AddNServiceBusFunctions() registers both function endpoints and send-only endpoints
• Updated integration app to use [NServiceBusSendOnlyFunction("client", Connection = "AzureWebJobsServiceBus")]

Send-only endpoint model

A send-only endpoint is defined with the [NServiceBusSendOnlyFunction] attribute on a static configuration method:

[NServiceBusSendOnlyFunction("client", Connection = "MyCustomConnection")]
public static void ConfigureClient(
    EndpointConfiguration endpointConfiguration,
    IServiceCollection services)
{
}

The Connection property holds the name of the configuration key (not the connection string value itself). When omitted, the transport uses its default connection name.

Supported method shape:

• must be static
• first parameter must be EndpointConfiguration
• optional additional parameters: IServiceCollection, IConfiguration, IHostEnvironment
• method name must match Configure{EndpointName} (case-insensitive)

Connection configuration flow

Both trigger-based and send-only endpoints now follow the same path for connection resolution:

Trigger-based: The Connection property on the trigger attribute (e.g. [ServiceBusTrigger(Connection = "...")]) is extracted by the source generator, flows through FunctionManifest.ConnectionSettingName, and is applied to the transport by the registration method.

Send-only: The Connection property on [NServiceBusSendOnlyFunction] is extracted by the source generator, flows through SendOnlyEndpointManifest.ConnectionSettingName, and is applied to the transport by the registration method.

Both manifests implement IConnectionSettingManifest, so the registration method uses a single helper to apply the connection setting name to the transport.

[andreasohlund]

@danielmarbach the source generation was not separated as expected, fixing that now

[andreasohlund]

I'm removing this

[andreasohlund]

@DavidBoike this needs some editorial love