Restrict currency pattern to upper-case letters only

Author: christiangmehling

src/components/schemas/generic/Currency.yaml

@@ -1,6 +1,6 @@
 description: Currency in ISO code format.
 type: string
-pattern: ^[a-zA-Z0-9]{3}$
+pattern: ^[A-Z]{3}$
 examples:
   - CHF
   - EUR