Now using class validator annotations

ref #3

src/models/Track.ts

@@ -1,14 +1,26 @@
 import { Entity, PrimaryGeneratedColumn, Column } from "typeorm";
+import {
+  IsInt,
+  IsNotEmpty,
+  IsOptional,
+  IsPositive,
+  IsString,
+} from "class-validator";
 
 @Entity()
 export class Track {
   @PrimaryGeneratedColumn()
+  @IsOptional()
+  @IsInt()
   id: number;
 
   @Column()
+  @IsString()
+  @IsNotEmpty()
   name: string;
 
-    //Length in meters
   @Column()
+  @IsInt()
+  @IsPositive()
   length: string;
 }