Oneshot accounts

Add lighter accounts that can be consumed only once.

Je n'ai pas encore fait les tests unitaires car la config de mock est assez longue à faire. Mais les tests d'intégration sont là.

Est-ce que l'ordre des deposit_event importe ? Si non, le code des calls peut être un peu factorisé sans coût.

end2end-tests/cucumber-features/oneshot_account.feature

+Feature: Oneshot account
+
+  Scenario: Simple oneshot consumption
+    When alice sends 8 ĞD to oneshot dave
+    Then alice should have 2 ĞD
+    Then dave should have oneshot 8 ĞD
+    When oneshot dave consumes into account bob
+    Then dave should have oneshot 0 ĞD
+    Then bob should have 18 ĞD
+    Then bob should have oneshot 0 ĞD
+
+  Scenario: Double oneshot consumption
+    When alice sends 8 ĞD to oneshot dave
+    Then alice should have 2 ĞD
+    Then dave should have oneshot 8 ĞD
+    When oneshot dave consumes 6 ĞD into account bob and the rest into oneshot charlie
+    Then dave should have oneshot 0 ĞD
+    Then bob should have 16 ĞD
+    Then bob should have oneshot 0 ĞD
+    Then charlie should have 10 ĞD
+    Then charlie should have oneshot 2 ĞD