DingTalkInboundMapper

Parses a DingTalk bot-message payload (Stream topic /v1.0/im/bot/messages/get or the HTTP callback body of the same protocol) into an InboundMessage.

Text messages (msgtype=text) map to their content. Media messages (picture / audio / video / file) map to a neutral marker text plus the ChannelMediaMetadata contract: the downloadCode and per-kind metadata are preserved verbatim, and exchanging the code for bytes (a server-side API call yielding a temporary download URL) is left to the application. Note the platform delivers audio/video/file to the robot in single chat only, not on group @-mention. richText and unknown types are returned as Optional#empty() so the caller can ack the event without dispatching to the agent.

Conversation kinds:

• conversationType="1" → DM (PeerKind#DIRECT). Peer id = sender staff id.

• conversationType="2" → group (PeerKind#GROUP). Peer id = conversation id.

Group messages typically arrive only when the bot is @-mentioned (DingTalk's bot SDK dispatches mention-triggered events only); the leading @bot text is preserved by the platform in text.content.