Write Booth\NotFoundException.php
Use Tests\Dependency
Write class Container.php, methods:
- register(string $key, Dependency|Closure). (Over)write dependency.
- has(string):bool check key presence
- get(string) returns key value. If closure returns retval. Throws the NotFoundException if unset. The exception message should be "Dependency not found" . $key
- singleton(string, Closure). Executes closure write value.