fix: Multiple "concurrent" calls to init causing multiple fetches.

[typotter]

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labels: mergeable

Fixes FF-3804

Motivation and Context

Eppo saw a dramatic increase in requests to the API and it was determined through investigation that multiple calls to init were being made before previous calls finished. Our code did not handle that case and would run the initialization workload (including fetching) for each init call until one of them resolved. This is bad because it causes additional network and CPU load for the client and increases the cost of delivery for Eppo.

Description

• Map of API Key => Promise
• init-wrapping method (init renamed to exclusiveInit and new method named init to preserve API).
• check the map for a value at the start of init and delegate if one exists.
• delete the value from the map when init completes - this indicates that the initialization workload is complete

How has this been tested?

• new tests

[typotter]

Thanks for the review, Felipe. ptal

[felipecsl]

🚢