code: public static MongoCredential createCredential(final String userName, final String database, final char[] password) {
          return new MongoCredential(null, userName, database, password);
      }
docs: Creates a MongoCredential instance with an unspecified mechanism.  The client will negotiate the best mechanism based on the
  version of the server that the client is authenticating to.
  
  <p>If the server version is 4.0 or higher, the driver will negotiate with the server preferring the SCRAM-SHA-256 mechanism. 3.x
  servers will authenticate using SCRAM-SHA-1, older servers will authenticate using the MONGODB_CR mechanism.</p>
  
  @param userName the user name
  @param database the database where the user is defined
  @param password the user's password
  @return the credential
  
  @since 2.13
  @mongodb.driver.manual core/authentication/#authentication-scram-sha-256 SCRAM-SHA-256
  @mongodb.driver.manual core/authentication/#authentication-scram-sha-1 SCRAM-SHA-1
  @mongodb.driver.manual core/authentication/#mongodb-cr-authentication MONGODB-CR