feature: add ses service to send notification emails

[itsmostafa]

Add initial dependencies for sending notification emails

🗣 Description

added AWS SDK for Go V2 to utilize SES for sending Con-PCA notification emails and STS for assuming user roles

💭 Motivation and context

Start initial work to build out an email manager for sending Notification emails for Con-PCA

🧪 Testing

tested code locally

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Add a tag or create a release.

[izzy64]

LGTM