fix(send): Simplify message sending interfaces

+ Update send methods to reduce variation and deprecated methods to reduce confusion.
+ Add tests for all send methods and updated docs.

BREAKING CHANGE: sendMessageByRoomId and sendMessageByRoom replaced with sendToRoomId and sendToRoom. sendMessage is now semantically used for the endpoint that sends a message object, where other send methods are abstractions of that and accept strings instead that are converted to a
message.