Get rid of all the RuntimeExceptions - It makes debugging and catching issues very complicated

[henrykuijpers]

I see a lot of usages of RuntimeException, it seems the library tries to avoid having to catch exceptions? However, it is of course very useful to catch any exceptions.

It's even very useful to introduce new checked exceptions and also more specific exceptions, for example a TokenLimitReachedException, CompletionTimeoutException, etc.