[Synchroniser] - Implement batch size config and retries strategy for Impressions

[emilianofant-split]

Javascript Slim Synchronizer

What did you accomplish?

In this PR, I'm adding the
a. Retries attempt per request and
b. Impression's Batch size configuration

• The config to determine the batch size of elements to POP from Storage (Events)
• Wrap the pop function into a function that can call itself recursively until there are no more elements in the Storage.
• Added CLI config and manager capability to create an Impressions Synchroniser with a custom batch size value.

... to the Impression Synchronizer. (Similar to #19 and #20)

ALSO, I've made some refactor to the retry function to be part of a utils file, where some helpers function may be placed.

How do we test the changes introduced in this PR?

1 - Checkout this branch:
git checkout efant_implementRetryImpressions
2 - Run unit tests
npm run test:unit

If you want to test it manually:
This file is a Custom Storage to connect with Redis, and can be used for manual tests.
For example:

npm run build && clear && ./dist/cli.js -k <A_VALID_APIKEY> -s ../path/to/inRedisStorage.cjs -r https://sdk.split-stage.io/api -e https://events.split-stage.io/api -p storagePrefix -impressionsPerPost 100 -maxRetries 4

Note the path to the Storage file

Related JIRA tickets and PRs

[Synchroniser] - Implement batch size config and retries strategy to Impressions

Extra Notes

[EmilianoSanchez]

LGTM