feat: RBAC authentication contract and role library

contracts/examples/RBACExample.sol

@@ -0,0 +1,61 @@
+pragma solidity ^0.4.8;
+
+import '../ownership/rbac/RBAC.sol';
+
+
+contract RBACExample is RBAC {
+
+    modifier onlyOwnerOrAdvisor()
+    {
+        require(
+            hasRole(msg.sender, "owner") ||
+            hasRole(msg.sender, "advisor")
+        );
+        _;
+    }
+
+    function RBACExample(address[] _advisors)
+        public
+    {
+        addRole(msg.sender, "owner");
+        addRole(msg.sender, "advisor");
+
+        for (uint256 i = 0; i < _advisors.length; i++) {
+            addRole(_advisors[i], "advisor");
+        }
+    }
+
+    function onlyOwnersCanDoThis()
+        onlyRole("owner")
+        view
+        external
+    {
+    }
+
+    function onlyAdvisorsCanDoThis()
+        onlyRole("advisor")
+        view
+        external
+    {
+    }
+
+    function eitherOwnerOrAdvisorCanDoThis()
+        onlyOwnerOrAdvisor
+        view
+        external
+    {
+    }
+
+    // owners can remove advisor's role
+    function removeAdvisor(address _addr)
+        onlyRole("owner")
+        public
+    {
+        // revert if the user isn't an advisor
+        //  (perhaps you want to soft-fail here instead?)
+        checkRole(_addr, "advisor");
+
+        // remove the advisor's role
+        removeRole(_addr, "advisor");
+    }
+}