character sets

[pshaughn]

Strings that aren't enumeration constants need to go over the network in these situations:

• usernames
• passwords
• input strings for game frames
• argument strings for game commands
• chat messages

Behavior for interesting strings in these cases needs to be well-defined and testable.

current situation:

• message is parsed from JSON, server hangs up on a client if it can't parse the client's message
• creating a user requires the username to be ascii alphanumeric
• input strings and command arguments are generated and used by playset code
• chat messages are (to be) implemented by taking an input element's value, sending it via JSON, and putting it in an element's textContent, with a filter on its string length as defined by Javascript String.prototype.length. This could raise various issues, but they should all be client-side issues and not require any particular server bulletproofing.

[pshaughn]

Username case-sensitivity is worth consideration here: if uSER exists, should usER be creatable? (currently yes)