private static byte[] serializeContext(Map<String, String> encryptionContext) {
    TreeMap<String, String> ordered = new TreeMap<>(encryptionContext);
    return ordered.toString().getBytes(UTF_8);
  }
A partial, fake implementation of AWSKMS that only supports encrypt and decrypt.

<p>It creates a new AEAD for every valid key ID. It can encrypt message for these valid key IDs,
but fails for all other key IDs. On decrypt, it tries out all its AEADs and returns the plaintext
and the key ID of the AEAD that can successfully decrypt it.
java_src/src/main/java/com/google/crypto/tink/integration/awskms/FakeAwsKms.java