chore: remove external clients api package

[Ang-m4]

Description

This PR removes the deprecated api_clients package, which has been replaced by the updated external_api_clients package. The changes include revising and sorting import statements and deleting the outdated package.

Testing

SMS Vendors

I sent an SMS to check if the service was available. Although I didn't receive the expected response, the 401 status code is enough proof that it's working.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Check if you are NOT addressing multiple issues with one PR. If is not the case continue the review process.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Check if you are NOT addressing multiple issues with one PR. If is not the case continue the review process.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Check if you are NOT addressing multiple issues with one PR. If is not the case continue the review process.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Check if you are NOT addressing multiple issues with one PR. If is not the case continue the review process.

[Ang-m4]

Since the changes in this PR exceed the recommended size of 1000 lines, I decided to split it into several smaller PRs that will be submitted soon. Additionally, I noticed an issue with the person_engine client package that needed to be addressed first.