Optimize and enable cache validation on Keycloak library

Currently the Keycloak library of Cloud Harness uses the cachetool `cached` decorator to cache some frequently called functions.

For some applications that want to read the latest data from Keycloak this library should support cache invalidation or pass through options

With the cachetools library we could implement a "invalidate cache" function

see https://cachetools.readthedocs.io/en/latest/#cachetools.cached

```
from cachetools import cached, TTLCache
from threading import Lock

# since we are using one cache, make it big enough (512K should be enough)
cache = TTLCache(maxsize=512*1024, getsizeof=len)
lock = Lock()

@cached(cache, ttl=30, lock=lock)
def some_func_to_get_data_from_keycloak(params):
#
return some result

# invalidate / clear cache
def clear_cache():
with lock:
cache.clear()
```