[FSSDK-11572] Python: Update impression event handling and send notification for global holdout

[esrakartalOpt]

Summary

• Update impression event handling
• Notification for global holdout
• Created new test cases for the impression event and notification
• Moved all holdout test cases to new file

Test plan

PR checks

Issues

• FSSDK-11572

[Mat001]

What Changed in PR #469:

-- decision_service.py - CHANGED
holdouts = project_config.get_holdouts_for_flag(feature.id) # ← Using ID now

-- project_config.py - CHANGED
def get_holdouts_for_flag(self, flag_id: str) -> list[HoldoutDict]:
return self.flag_holdouts_map.get(flag_id, []) # ← Looking up by ID

What DIDN'T Change:

-- project_config.py init - NOT CHANGED (still in codebase)
if applicable_holdouts:
self.flag_holdouts_map[feature.key] = applicable_holdouts # ← Still using KEY!

The Problem:

-- Map is built with KEYS:
flag_holdouts_map = {
"checkout_flag": [holdout1, holdout2], # ← Key = "checkout_flag"
"payment_flow": [holdout3] # ← Key = "payment_flow"
}

-- Code is looking up by IDs:
holdouts = flag_holdouts_map.get("123456", []) # ← ID = "123456"
-- Result: [] (empty!) because "123456" != "checkout_flag"

Impact: Holdouts will NEVER be found. All lookups return empty list. Holdout decisions
will never happen.

[Mat001]

Also consistency issue:

• JavaScript SDK uses flag KEY consistently
• Python PR changes to flag ID
• This breaks cross-SDK consistency

[Mat001]

looks good now!