createChannelMembership  
  inline suspend fun ChimeSdkMessagingClient.createChannelMembership(crossinline block: CreateChannelMembershipRequest.Builder.() -> Unit): CreateChannelMembershipResponse
Adds a member to a channel. The InvitedBy field in ChannelMembership is derived from the request header. A channel member can:
- List messages 
- Send messages 
- Receive messages 
- Edit their own messages 
- Leave the channel 
Privacy settings impact this action as follows:
- Public Channels: You do not need to be a member to list messages, but you must be a member to send messages. 
- Private Channels: You must be a member to list or send messages. 
The x-amz-chime-bearer request header is mandatory. Use the ARN of the AppInstanceUserArn or AppInstanceBot that makes the API call as the value in the header.