HttpTrigger attribute on custom model isn't rendered

**Describe the issue**
As per Microsoft documentation, the HttpTrigger attribute can be placed on a custom model instead the HttpRequest.
If this is **not** the first parameter in the function then the method is ignored when generating the OpenApi/swagger spec.

[Edit]
If the HttpTrigger is **not** annotated on the first parameter, regardless of whether it is a custom model or the HttpRequest, the method is ignored.

**To Reproduce**
Create a Function with an HttpTrigger attribute on a custom type, first parameter.
Create a Function with an HttpTrigger attribute on a custom type, second parameter, with the first being `HttpRequest.`

**Expected behavior**
Both endpoints should be visible in the OpenApi spec

```
[FunctionName(nameof(GetThing))]
public async Task GetThing(
[HttpTrigger(AuthorizationLevel.Function, "GET", Route = "thing/{id:int}")]
HttpRequest req,
int id,
ExecutionContext context) { }

[FunctionName(nameof(CreateThing))]
public async Task CreateThing(
HttpRequest req,
[HttpTrigger(AuthorizationLevel.Function, "POST", Route = "thing")]
Thing thing,
ExecutionContext context) { }
```

Start by reproducing the two Function signatures described in the issue, with HttpTrigger on the first and second parameters, and compare the generated OpenAPI/Swagger spec. Done means both endpoints are visible in the spec, including the endpoint using a custom model.

Written by the indexing model from the issue text.