@CanIgnoreReturnValue
  @GuardedBy("this")
  public synchronized AndroidKeysetManager add(KeyTemplate keyTemplate)
      throws GeneralSecurityException {
    keysetManager = keysetManager.add(keyTemplate);
    write(keysetManager.getKeysetHandle(), writer, masterAead);
    return this;
  }
Generates and adds a fresh key generated using {@code keyTemplate}.

@throws GeneralSecurityException if cannot find any {@link KeyManager} that can handle {@code
    keyTemplate}
java_src/src/main/java/com/google/crypto/tink/integration/android/AndroidKeysetManager.java