Explore if `validate_access` can be expressed as a decorator

This is potentially possible with the following type of pattern, where `new_f` performs a validation and only executes `f` if validation succeeds.

```python
In [20]: def bar(f):
...: def new_f(a, b):
...: if a > 5:
...: print("valid")
...: return f(a+5, b+5)
...: else:
...: print("invalid")
...: return None # or some failure function or whatever
...: return new_f
...:

In [21]: @bar
...: def foo(a, b):
...: print(a, b)
...:

In [22]: foo(3, 10)
invalid

In [23]: foo(6, 10)
valid
11 15
```

However, connexion injects other decorators so it is possible this will not work hence an exploration first.

No file or test is named. Start by locating the current validate_access implementation and tracing how Connexion applies its decorators and passes arguments. Done means establishing whether the decorator approach is compatible and documenting the resulting implementation scope or constraints.

Written by the indexing model from the issue text.