Agora RTC Objective-C API Reference Refactor

Here is a list of all namespace members with links to the namespace documentation for each member:

### - d -

- DEFAULT_CONNECTION_ID : agora::rtc
- DEFAULT_LOG_SIZE_IN_KB : agora::commons
- DEFAULT_MIN_BITRATE : agora::rtc
- DEFAULT_MIN_BITRATE_EQUAL_TO_TARGET_BITRATE : agora::rtc
- DEGRADATION_PREFERENCE : agora::rtc
- DIRECT_CDN_STREAMING_ERROR : agora::rtc
- DIRECT_CDN_STREAMING_ERROR_AUDIO_PUBLICATION : agora::rtc
- DIRECT_CDN_STREAMING_ERROR_BAD_NAME : agora::rtc
- DIRECT_CDN_STREAMING_ERROR_FAILED : agora::rtc
- DIRECT_CDN_STREAMING_ERROR_NET_CONNECT : agora::rtc
- DIRECT_CDN_STREAMING_ERROR_OK : agora::rtc
- DIRECT_CDN_STREAMING_ERROR_VIDEO_PUBLICATION : agora::rtc
- DIRECT_CDN_STREAMING_STATE : agora::rtc
- DIRECT_CDN_STREAMING_STATE_FAILED : agora::rtc
- DIRECT_CDN_STREAMING_STATE_IDLE : agora::rtc
- DIRECT_CDN_STREAMING_STATE_RECOVERING : agora::rtc
- DIRECT_CDN_STREAMING_STATE_RUNNING : agora::rtc
- DIRECT_CDN_STREAMING_STATE_STOPPED : agora::rtc
- DISABLE_SIMULCAST_STREAM : agora::rtc
- DISABLED : agora::rtc
- DUMMY_CONNECTION_ID : agora::rtc