New endpoints for foreign currencies in expense applications on freee Accounting API

Changes

• GET /api/1/expense_applications/currencies retrieves a list of foreign currencies for expense applications.
• POST /api/1/expense_applications/currencies creates a foreign currency for expense applications.
• GET /api/1/expense_applications/currencies/{id} retrieves a foreign currency for expense applications.
• PUT /api/1/expense_applications/currencies/{id} updates a foreign currency for expense applications.
• DELETE /api/1/expense_applications/currencies/{id} deletes a foreign currency for expense applications.

Affected areas

GET /api/1/expense_applications/currenciesPOST /api/1/expense_applications/currenciesGET /api/1/expense_applications/currencies/{id}PUT /api/1/expense_applications/currencies/{id}DELETE /api/1/expense_applications/currencies/{id}