[AXS-24] PAP API

[bernardoaraujor]

Policy Administration Point manages updates to policies and determines which policies apply to what requests.

PAP directory structure on repository must look like the following:

access/pap/
├── pap.c
├── pap.h
├── user
│   ├── user.c
│   └── user.h
└── validator
    ├── validator.c
    └── validator.h

API Requirements:

• PAP API must consume custom callbacks for Policy Store in a platform agnostic way.
• PAP header (access/pap/pap.h) must expose functions to be used by Access Supervisor.

Related issues: https://github.com/iotaledger/access/issues/50 https://github.com/iotaledger/access/issues/47

JIRA: AXS-24

[strahinjagolic]

Done in 99ab331d3ee8010852ca90a713a9de4478b6f8bc