v0.3.12

Remove CNSA2. Beacon rejects signed payloads with unexpected key ID. Specify that the registration process must use a plaintext, and that the server will insert one if not otherwise provided. Delete beacon crypto state on failure to read appCipherText on final leg of registration. Sign and Kem key decoding now check that the buffer matches an expected type. Add CTX commitment scheme from Chan and Rogaway. Add rust example