A new delete action for account level Chat Channels APIs. Enhancements include a Chat Files API new request field to post personal chats, and a new Chat Channels API request field for a shared space.

New Chat Channels API and enhancements to Chat Files and Chat Channels APIs

## Added
- New **Chat Channels (Account-level)** API:
	- `DELETE /v2/chat/users/{userId}/channels/{channelId}/members`
## Enhancements
- New `postToPersonalChat` request field in the following  **Chat Files** API:
	- `POST /v2/chat/users/{userId}/files`
- New `shared_space` request field in the following  **Chat Channels** API:
	- `POST /v2/chat/users/{userId}/channels`
