Add CLICS API end point: /access

[lane55]

Is your feature request related to a problem?

Non-compliance with CLICS API Spec.

Feature Description:

Implement an access end point.
Create a "empty" return value, empty JSON array.

See spec at: https://ccs-specs.icpc.io/2022-07/contest_api#access

Have you considered other ways to accomplish the same thing?

There are none.

Do you have any specific suggestions for how your feature would be implemented in PC^2?

Add endpoint /contests//access with empty array, i.e. {}

Additional context:

[lane55]

Again, at first implement by just returning a empty array.