Issue:
deps(common_utils): put the async ext trait behind a feature

## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [x] Dependency updates

## Description
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This PR puts the `AsyncExt` trait and certain async functions in the `common_utils` crate behind a feature flag.

### Additional Changes
None
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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2. `crates/router/src/configs`
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## Motivation and Context
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Required to make the `api_models` crate free of any async-relate dependencies.

## How did you test it?
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Did you write an integration/unit/API test to verify the code changes?
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cargo build + cargo hack

## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable


Resolution:
<think>
PR Context:
- Title: Changelog for release v0.5.5
- Merged: 2023-04-11T07:30:11Z
- Files changed: 1 files
- Commits: 1 commits

Implementation approach:
# 0.5.5 (2023-04-10)

## New Features

* **api_models:**  derive `strum::Display` for `RefundStatus` (#846) (4524d4f5)
*  allow (de)serializing countries to/from alpha-2, alpha-3 and numeric country codes (#836) (899767cf)
* **connector:**  add authorize, capture, void, psync, refund, rsync for PayPal connector (#747) (36049c13)

## Bug Fixes

*  Add locker sign keyid in env (#844) (70dff140)

## Other Changes

* **common_utils:**  put the async ext trait behind a feature (#835) (d
</think>

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