renamed models, added mapper for recipes

frontend/src/models/ServingsModel.ts

@@ -0,0 +1,12 @@
+/**
+ * Defines how many servings of the dish are prepared when following the recipe
+ */
+
+export interface ServingsModel{
+    /** Amount of servings */
+    amount: number,
+
+    /** Unit, e.g. 4 persons, 2 glasses, 12 cupcakes */
+    unit: string
+
+}