Add _ninja_ignore_args support for dependency injection

[arjandepooter]

Summary

Adds support for _ninja_ignore_args attribute to enable dependency injection patterns in Django Ninja view functions.

Problem

When using decorators that inject dependencies as function arguments, Django Ninja tries to process these injected arguments as API parameters, causing them to appear in the OpenAPI schema and parameter validation. This breaks clean dependency injection patterns.

Solution

• Add _ninja_ignore_args attribute support in ViewSignature processing
• Arguments listed in this attribute are skipped during signature analysis
• Add ignore_args() utility function for convenience
• Maintains full backward compatibility

Example Usage

def inject_service(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        kwargs["service"] = MyService()
        return func(*args, **kwargs)
    
    wrapper._ninja_ignore_args = ["service"]
    return wrapper

@api.get("/endpoint")
@inject_service  
def my_view(request, param: str, service: MyService):
    return service.process(param)

The service parameter is injected by the decorator but ignored by Django Ninja's parameter processing.

Testing

Added integration test test_ninja_ignore_args_integration() that demonstrates the complete flow including dependency injection, runtime functionality, and OpenAPI schema validation.