Use Operations in CreateCertificateCommand

[DechengMa]

We have implemented the CreateCertificateCommand, this PR is to apply Operations (our new way of fetching data) to this command

📝 Summary of Changes

Changes proposed in this pull request:

• Add function createCertificate to AppStoreConnectService
• Create struct CreateCertificateOperation and CreateCertificateOptions
• Apply these to CreateCertificateCommand

🧐🗒 Reviewer Notes

💁 Example

Usage:

asc certificates create [--api-issuer <uuid>] [--api-key-id <keyid>] [--csv] [--json] [--table] [--yaml] <certificate-type> <csr-file>

🔨 How To Test

swift run asc certificates create MAC_INSTALLER_DISTRIBUTION filePath

[adamjcampbell]

@DechengMa this PR needs to be updated as I converted the command to make use of await

[DechengMa]

@DechengMa this PR needs to be updated as I converted the command to make use of await

Hi @adamjcampbell , I have rebased master and added .await() to the command