Add doc comment

Author: sgreenbury

trustchain-core/src/lib.rs

@@ -31,4 +31,5 @@ pub const TRUSTCHAIN_PROOF_SERVICE_ID_VALUE: &str = "trustchain-controller-proof
 /// The value of the type for the service containing a Trustchain controller proof within a DID document.
 pub const TRUSTCHAIN_PROOF_SERVICE_TYPE_VALUE: &str = "TrustchainProofService";
 
+/// String slice for JSON file extension for consistency.
 pub const JSON_FILE_EXTENSION: &str = ".json";

trustchain-ion/src/lib.rs

@@ -168,6 +168,7 @@ pub enum TrustchainBitcoinError {
 pub const CONTROLLER_KEY: &str = "controller";
 pub const CREATE_OPERATION_FILENAME_PREFIX: &str = "create_operation_";
 pub const ATTEST_OPERATION_FILENAME_PREFIX: &str = "attest_operation_";
+// TODO: uncomment when update operation functionality merged
 // pub const UPDATE_OPERATION_FILENAME_PREFIX: &str = "update_operation_";
 
 // ION