Added a delegate relation for the banking example

stores/banking/README.md

@@ -2,7 +2,7 @@
 
 ## Use-Case
 
-It models a banking system, with account managers and account owners, where they have different limits for doing bank transactions. The limit can be overruled for a specific transaction.
+It models a banking system with account managers and account owners, each having different transaction limits. A specific transaction's limit can be overruled when necessary. An account owner can delegate access to other users.
 
 The model, tuples and unit tests are detailed in [store.fga.yaml](./store.fga.yaml).
 

stores/banking/store.fga.yaml

@@ -3,6 +3,7 @@ model: |
     schema 1.1
 
   type employee
+
   type customer
 
   # We need a global Bank type where we define all customers and the transfer limit policy 
@@ -22,8 +23,11 @@ model: |
       define owner : [customer] 
       define account_manager : [employee]
 
+      # The customer can delegate access to another customer
+      define delegate: [customer]
+
       # The bank transfer permission is conditioned to the policy assigned to customers or account managers.
-      define can_make_bank_transfer : (owner or account_manager) and transfer_limit_policy from bank
+      define can_make_bank_transfer : (owner or account_manager or delegate) and transfer_limit_policy from bank
 
   # The policy has a maximum limit depending that can be overruled for a specific transaction.
   condition transfer_limit_policy(transaction_amount: double, transaction_limit: double, new_transaction_limit_approved: double) {
@@ -54,6 +58,11 @@ tuples:
     relation: customer
     object: bank:acme
 
+  # Peter is bank Acme's customer
+  - user: customer:peter
+    relation: customer
+    object: bank:acme
+
   # Anne is bank Acme's employee that's an account manager
   - user: employee:bob
     relation: account_manager
@@ -74,6 +83,11 @@ tuples:
     relation: account_manager
     object: account:123
 
+  # Peter is a delegate for the `123` account 
+  - user: customer:peter
+    relation: delegate
+    object: account:123
+
 tests:
   - name: Test bank transfers from customers
     check:
@@ -84,7 +98,15 @@ tests:
         new_transaction_limit_approved : 0
       assertions:
         can_make_bank_transfer: true
-
+
+    - user: customer:peter
+      object: account:123
+      context: 
+        transaction_amount: 10
+        new_transaction_limit_approved : 0
+      assertions:
+        can_make_bank_transfer: true
+
     - user: customer:anne
       object: account:123
       context: