Refactor cache clearing logic into EventCacheHelper

[iamacook]

Summary

Resolves #1926

Our HooksRepository['onEventClearCache'] covers cache clearing based on every event from the Transaction Service and Config. Service and is therefore excessively long. Considering we also have a similar class for notification-enabled hooks, this logic was duplicated.

This adds a new EventCacheHelper, breaking down respective event logic into a separate method. It is then used in both the (non-)event based hook repositories.

Changes

• Extract cache-related logic to EventCacheHelper
• Use EventCacheHelper in HooksRepository and HooksRepositoryWithNotifications
• Update tests accordingly

[coveralls]

Pull Request Test Coverage Report for Build 10937273807

Details

• 84 of 84 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 90.762%

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Totals
Change from base Build 10906426126:	0.1%
Covered Lines:	8312
Relevant Lines:	8784

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💛 - Coveralls