Add ability to import aws_iam_user_ssh_key

[AMeng]

Changes proposed in this pull request:

• Add ability to import aws_iam_user_ssh_key
• Ignore newlines and comments in aws_iam_user_ssh_key.public_key diffs

While testing importing, I noticed that AWS strips out any comments in SSH formatted keys. Comments are anything after the key itself (usually a username or email). I think it makes sense to ignore these since they're extremely common, and Terraform will perpetually think there is a diff if present. I also ignored newlines since AWS strips those as well.

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccAWSUserSSHKey'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -parallel 20 -run=TestAccAWSUserSSHKey -timeout 120m
?   	github.com/terraform-providers/terraform-provider-aws	[no test files]
=== RUN   TestAccAWSUserSSHKey_basic
=== PAUSE TestAccAWSUserSSHKey_basic
=== RUN   TestAccAWSUserSSHKey_pemEncoding
=== PAUSE TestAccAWSUserSSHKey_pemEncoding
=== CONT  TestAccAWSUserSSHKey_basic
=== CONT  TestAccAWSUserSSHKey_pemEncoding
--- PASS: TestAccAWSUserSSHKey_pemEncoding (12.66s)
--- PASS: TestAccAWSUserSSHKey_basic (12.90s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	15.713s

[bflad]

LGTM, thanks @AMeng 🚀

--- PASS: TestAccAWSUserSSHKey_pemEncoding (8.50s)
--- PASS: TestAccAWSUserSSHKey_basic (9.17s)

[bflad]

This has been released in version 1.52.0 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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