We use `certificateAuthority(int)` to create certificates that can sign other certificates. The
int specifies how many intermediate certificates are allowed beneath it in the chain.

```java
HeldCertificate rootCertificate = new HeldCertificate.Builder()
    .certificateAuthority(1)
    .build();

HeldCertificate intermediateCertificate = new HeldCertificate.Builder()

      HeldCertificate
        .Builder()
        .serialNumber(1L)
        .certificateAuthority(1)
        .commonName("root")
        .addSubjectAlternativeName("root_ca.com")
        .build()
    serverIntermediateCa =
      HeldCertificate
        .Builder()
        .signedBy(serverRootCa)
        .certificateAuthority(0)
        .serialNumber(2L)
        .commonName("intermediate_ca")

    builder = builder.keyPair(keyPair)
    builder = builder.keyPair(keyPair.public, keyPair.private)
    builder = builder.signedBy(HeldCertificate.Builder().build())
    builder = builder.certificateAuthority(0)
    builder = builder.ecdsa256()
    builder = builder.rsa2048()
    val heldCertificate: HeldCertificate = builder.build()
  }

  @Test
  fun javaNetAuthenticator() {