Custom Function Attributes for function categorization

#### What problem would the feature you're requesting solve? Please describe.
I want to categorize my function app functions and use that categorization to make decisions in my custom middleware.

#### Describe the solution you'd like
I want to add metadata to my functions via a custom attribute that would be available in the `FunctionDefinition` class via a custom attribute. Something like the following `MyCustomAttribute`:

```
[MyCustomAttribute("Classification1")
[Function("MyTestFunction")]
public IActionResult MyTestFunction([HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = null)] HttpRequest request) => new OkObjectResult("Successfully reached API");
```

#### Describe alternatives you've considered

I've tried creating a custom Attribute by inheriting `System.Attribute` and applying the attribute to my function, but I don't see the attribute data included in the FunctionContext.

I've also considered listing all of my functions by name in my middleware and using the existing `FunctionContext.FunctionDefinition.Name` value to determine what action to take based on the name. This is not ideal because it requires me to update the middleware every time I add a new function.