AS: Add API to set policy

[jialez0]

No description provided.

[Xynnn007]

Thanks for the API! It is very useful!

[niteeshkd]

It seems the API updates the existing opa policy file (e.g. .../opa/policy.rego).

1. Can it be used to create a new policy file and use that in the policy evaluation? I think coco owner may provide different policy files for different cocos while using the same attestation service.
2. If later some other type of policy engine is supported, is it expected that new API will be created to update the policy for that type of policy engine?

[jialez0]

It seems the API updates the existing opa policy file (e.g. .../opa/policy.rego).

1. Can it be used to create a new policy file and use that in the policy evaluation? I think coco owner may provide different policy files for different cocos while using the same attestation service.
2. If later some other type of policy engine is supported, is it expected that new API will be created to update the policy for that type of policy engine?

@niteeshkd Thanks for proposal! I will try to think and design to implement the functions you mentioned.

[jialez0]

@niteeshkd I have updated the code, now set policy input specified the policy type and policy ID, you can take a look at this PR again. Thanks!
In this PR, we only use "default" as the policy ID for now, this is because how KBS/AS identifies coco resources is still under discussion and design. After we have a comprehensive mechanism to identify the coco resources, we can use different policy IDs based on that ID.

[niteeshkd]

@niteeshkd I have updated the code, now set policy input specified the policy type and policy ID, you can take a look at this PR again. Thanks! In this PR, we only use "default" as the policy ID for now, this is because how KBS/AS identifies coco resources is still under discussion and design. After we have a comprehensive mechanism to identify the coco resources, we can use different policy IDs based on that ID.

Sounds good to me !