Added support for VPC-based connectivity

[madhavvishnubhatta]

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the library.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

Description

Relations

Closes #45250

References

https://aws.amazon.com/blogs/aws/aws-transfer-family-sftp-connectors-now-support-vpc-based-connectivity/
https://docs.aws.amazon.com/cli/latest/reference/transfer/create-connector.html
https://docs.aws.amazon.com/cli/latest/reference/transfer/update-connector.html

Output from Acceptance Testing

% make testacc PKG=transfer TESTS=TestAccTransferConnector
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
make: Running acceptance tests on branch: 🌿 f-vpc_support_for_sftp_connector 🌿...
TF_ACC=1 go1.24.10 test ./internal/service/transfer/... -v -count 1 -parallel 20 -run='TestAccTransferConnector'  -timeout 360m -vet=off
2025/12/01 12:03:30 Creating Terraform AWS Provider (SDKv2-style)...
2025/12/01 12:03:30 Initializing Terraform AWS Provider (SDKv2-style)...
=== RUN   TestAccTransferConnectorDataSource_basic
=== PAUSE TestAccTransferConnectorDataSource_basic
=== RUN   TestAccTransferConnectorDataSource_egressConfig
=== PAUSE TestAccTransferConnectorDataSource_egressConfig
=== RUN   TestAccTransferConnector_basic
--- PASS: TestAccTransferConnector_basic (25.76s)
=== RUN   TestAccTransferConnector_sftpConfig
--- PASS: TestAccTransferConnector_sftpConfig (15.87s)
=== RUN   TestAccTransferConnector_securityPolicyName
--- PASS: TestAccTransferConnector_securityPolicyName (15.80s)
=== RUN   TestAccTransferConnector_disappears
--- PASS: TestAccTransferConnector_disappears (13.99s)
=== RUN   TestAccTransferConnector_egressConfig
--- PASS: TestAccTransferConnector_egressConfig (78.60s)
=== RUN   TestAccTransferConnector_egressConfigUpdate
--- PASS: TestAccTransferConnector_egressConfigUpdate (76.69s)
=== RUN   TestAccTransferConnector_tags
--- PASS: TestAccTransferConnector_tags (35.41s)
=== CONT  TestAccTransferConnectorDataSource_basic
=== CONT  TestAccTransferConnectorDataSource_egressConfig
--- PASS: TestAccTransferConnectorDataSource_basic (13.67s)
--- PASS: TestAccTransferConnectorDataSource_egressConfig (88.10s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/transfer   350.406s

[github-actions]

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[github-actions]

✅ Thank you for correcting the previously detected issues! The maintainers appreciate your efforts to make the review process as smooth as possible.