Hi matrixebiz,
I'm not sure if I understand the question correctly, but it seems like you want to append a ID token key to the end of a url?
If the ID token key is of type string, then you can simply do stream.url = stream.url + ID Key like you stated.
If the ID token key is of type integer, then you can use the .toStr() function to convert the integer into a string like so:
stream.url = stream.url + ID_TOKEN_VARIABLE.toStr()
This is assuming that stream.url is the HLS stream url as a string and the ID_TOKEN_VARIABLE is an integer/float.
https://sdkdocs.roku.com/display/sdkdoc/ifIntOpsIf not, the quickest way to go about checking how to append things would be to use the debugger as a REPL to figure out how things work:
You can create a breakpoint in your code by inserting a "stop" in the code where you want to break, telnet to the debugging port 8085/8089 on your Roku device and see what the types of the variable are by running "type(stream.url)" or type(VARIABLE) to check.
Hope that helps! Let me know if that was what you were asking or if you have any additional questions.