Make message host level configurations configurable per function

[apranaseth]

In hosts.json, under message options below configurations can be set. With this feature, the user will be able to set them per function as well. This way within the same job host (WebJobs or Functions), different functions could be defined with flavors for autocomplete or controlling the complete on its own in the function code.

"messageHandlerOptions": {
"autoComplete": true,
"maxConcurrentCalls": 32,
"maxAutoRenewDuration": "00:05:00"
},

[mathewc]

The work here would be to identify the set of primitive type config options from MessageHandlerOptions that we'd need to promote to ServiceBusTriggerAttribute (e.g. AutoComplete, MaxAutoRenewDuration, MaxConcurrentCalls), since you can't use non-constant types in attributes like this:

public static async Task ProcessMessage(
    [ServiceBusTrigger("myqueue", Connection = "ServiceBusConnection", 
    MessageHandlerOptions = new MessageHandlerOptions { AutoComplete = false })] 
    string myQueueItem,
    Int32 deliveryCount,
    DateTime enqueuedTimeUtc,
    string messageId,
    ILogger log)

So we'd have to have:

public static async Task ProcessMessage(
    [ServiceBusTrigger("myqueue", Connection = "ServiceBusConnection"), AutoComplete = false, MaxConcurrentCalls = 16] 
    string myQueueItem,
    Int32 deliveryCount,
    DateTime enqueuedTimeUtc,
    string messageId,
    ILogger log)

Similarly, if we want to also allow this for SessionHandlerOptions, we'd be looking at properties (AutoComplete, MaxAutoRenewDuration, MaxConcurrentSessions, MessageWaitTimeout). Like other option types that are both host/function level (e.g. FunctionTimeout) we'd have to handle these hierarchically and apply the host level first, then function level.

It does mean that we're a middleman then, responsible for copying this config ourselves onto the SB SDK types, so have to maintain this going forward, and expose any new properties they add in the future.