Eat mimecraft.

```
  /** Creates a new multipart builder that uses a random boundary token. */
  public MultipartBuilder() {
    this(UUID.randomUUID().toString());
  }

  /**
   * Creates a new multipart builder that uses {@code boundary} to separate
   * parts. Prefer the no-argument constructor to defend against injection
   * attacks. 
   */
  public MultipartBuilder(String boundary) {
    this.boundary = boundary;
  }
```