feat: Implement admin get roles API endpoint

packages/backend/test/mocks/rest/api/v1/admin/roles/get-roles.ee.js

@@ -0,0 +1,26 @@
+const getRolesMock = async (roles) => {
+  const data = roles.map((role) => {
+    return {
+      id: role.id,
+      key: role.key,
+      name: role.name,
+      isAdmin: role.isAdmin,
+      description: role.description,
+      createdAt: role.createdAt.toISOString(),
+      updatedAt: role.updatedAt.toISOString(),
+    };
+  });
+
+  return {
+    data: data,
+    meta: {
+      count: data.length,
+      currentPage: null,
+      isArray: true,
+      totalPages: null,
+      type: 'Role',
+    },
+  };
+};
+
+export default getRolesMock;