Feature: add support for followers endpoint

[takanome-dev]

Type of feature

🍕 Feature

Current behavior

Currently, we don't have a way to get the list of user's followers, but there is a way to get the list of user's following. https://beta.api.opensauced.pizza/#/User%20service/getFollowingListByUsername

This is related to https://github.com/open-sauced/app/issues/1452

Suggested solution

No response

Additional context

No response

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