Implemented more stats endpoints

ref #56

src/models/entities/RunnerGroup.ts

@@ -44,4 +44,20 @@ export abstract class RunnerGroup {
    */
   @OneToMany(() => Runner, runner => runner.group, { nullable: true })
   runners: Runner[];
+
+  /**
+   * Returns the total distance ran by this group's runners based on all their valid scans.
+  */
+  @IsInt()
+  public get distance(): number {
+    return this.runners.reduce((sum, current) => sum + current.distance, 0);
+  }
+
+  /**
+   * Returns the total donations a runner has collected based on his linked donations and distance ran.
+  */
+  @IsInt()
+  public get distanceDonationAmount(): number {
+    return this.runners.reduce((sum, current) => sum + current.distanceDonationAmount, 0);
+  }
 }