year & month replaced by yearMonth object

app/lib/db-types.ts

@@ -9,6 +9,11 @@ export interface BillAttachment {
     fileContentsBase64: string;
 };
 
+export interface YearMonth {
+    year: number;
+    month: number;
+};
+
 /** bill object in the form returned by MongoDB */
 export interface BillingLocation {
     _id: string;
@@ -18,10 +23,8 @@ export interface BillingLocation {
     userEmail?: string | null;
     /** name of the location */
     name: string;
-    /** billing period year */
-    year: number;
-    /** billing period month */
-    month: number;
+    /** billing period year and month */
+    yearMonth: YearMonth;
     /** array of bills */
     bills: Bill[];
     /** (optional) notes */