Ajout du cache sur les appels pour les stats

Et appel à l'API sur l'affichage de l'onglet

Front/skydivelogs-app/src/services/service-cache-api.service.ts

@@ -0,0 +1,37 @@
+import { Injectable } from '@angular/core';
+import { Observable } from 'rxjs/Observable';
+import { tap } from 'rxjs/operators';
+import { CacheApiKey } from '../models/cache-api-key.enum';
+import { of } from 'rxjs';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class ServiceCacheApi {
+  private cache: Map<CacheApiKey, Observable<any>>;
+
+  constructor() { 
+    this.cache = new Map<CacheApiKey, Observable<any>>();
+  }
+
+  public get<T>(key: CacheApiKey, callToApi: Observable<T>, withResetCache: boolean = false) : Observable<T> {
+    if (withResetCache === true) {
+      this.cache.delete(key);
+    }
+
+    const cached = this.cache.get(key);
+
+    if (cached) {
+      return cached;
+    } else {
+      return callToApi.pipe(
+                        tap(event => { 
+                          this.cache.set(key, of(event));
+                        }));
+    }
+  }
+
+  public delete(key: CacheApiKey) {
+    this.cache.delete(key);
+  }
+}