Message extras are a way to allow messages to contain data other than just a message, such as an image attachment, polls, fancy formatting, particle effects, etc.
Message extras allow for a file to be uploaded, and arbitrary json appended to the message.
This arbitrary json should only be checked serverside for validity, as clients may want to add their own extras outside of the standard, or allow nonstandard clients to communicate.
Message extras can also allow the message to be tagged as hidden, just for data transfer, again for unstandard clients.
Message extras are a way to allow messages to contain data other than just a message, such as an image attachment, polls, fancy formatting, particle effects, etc.
Message extras allow for a file to be uploaded, and arbitrary json appended to the message. This arbitrary json should only be checked serverside for validity, as clients may want to add their own extras outside of the standard, or allow nonstandard clients to communicate.
Message extras can also allow the message to be tagged as hidden, just for data transfer, again for unstandard clients.