feat: new homepage statistic API's (#167)

* add date format and orDefault helpers

* introduce new statistics calculations queries

* rework statistics endpoints

* code generation

* fix styles on photo card

* label and location aggregation endpoints

* code-gen

* cleanup parser and defaults

* remove debug point

* setup E2E Testing

* linters

* formatting

* fmt plus name support on time series data

* code gen

frontend/lib/api/classes/stats.ts

@@ -0,0 +1,42 @@
+import { BaseAPI, route } from "../base";
+import { GroupStatistics, TotalsByOrganizer, ValueOverTime } from "../types/data-contracts";
+
+function YYYY_DD_MM(date?: Date): string {
+  if (!date) {
+    return "";
+  }
+  // with leading zeros
+  const year = date.getFullYear();
+  const month = (date.getMonth() + 1).toString().padStart(2, "0");
+  const day = date.getDate().toString().padStart(2, "0");
+  return `${year}-${month}-${day}`;
+}
+export class StatsAPI extends BaseAPI {
+  totalPriceOverTime(start?: Date, end?: Date) {
+    return this.http.get<ValueOverTime>({
+      url: route("/groups/statistics/purchase-price", { start: YYYY_DD_MM(start), end: YYYY_DD_MM(end) }),
+    });
+  }
+
+  /**
+   * Returns ths general statistics for the group. This mostly just
+   * includes the totals for various group properties.
+   */
+  group() {
+    return this.http.get<GroupStatistics>({
+      url: route("/groups/statistics"),
+    });
+  }
+
+  labels() {
+    return this.http.get<TotalsByOrganizer[]>({
+      url: route("/groups/statistics/labels"),
+    });
+  }
+
+  locations() {
+    return this.http.get<TotalsByOrganizer[]>({
+      url: route("/groups/statistics/locations"),
+    });
+  }
+}