mongoc_uri_option_is_utf8() reports true for "authMechanism", but mongoc_uri_set_option_as_utf8() is not suitable for setting that option. Based on the static mongoc_uri_parse_option() function, its value must be appended to uri->credentials instead of uri->options.

"authMechanismProperties" also cannot be set, since mongoc_uri_parse_auth_mechanism_properties() is static.

The PHP and HHVM drivers depend on being able to set URI options individually, since they allow options to be received in a separate array to be merged atop the values in the URI string.