Improve feedback on missing rule_set argument

[HugoPerrier]

Is your feature request related to a problem? Please describe

When the RulesEngine.apply_rules method is ran, if the rule_set argument is missing,
A KeyError is raised with the message
KeyError: "Rule set 'None' not found in the rules, available rule sets are : ['my_rule_set']."

This does not make it clear that you should set the rule_set argument

Describe the solution you'd like

• Making the rule_set a mandatory argument (state that you should type "default to use the default rule set?)

Describe alternatives you've considered

• Make the error message Clearer

[develop-cs]

Hi,
Currently, the rule is:

arta/src/arta/_engine.py

Lines 234 to 237 in 65f0a66

	# If there is no given rule set param. and there is only one rule set in self.rules
	# and its value is 'default_rule_set', look for this one (rule_set='default_rule_set')
	if rule_set is None and len(self.rules) == 1 and self.rules.get(self.CONST_DFLT_RULE_SET_ID) is not None:
	rule_set = self.CONST_DFLT_RULE_SET_ID

The goal is to prevent any misuse of a rule set when there are several in the configuration.

But it can change of course.

What do you think about a simpler (and backward compatible) solution: rule_set: str = "default_rule_set" in the apply_rules() definition?