In most cases private keys are used to produce certs and cert requests,
but there are some less-common cases where the PEM-formatted keypair is
used alone. The public_key_pem attribute supports such cases.
This also includes a public_key_openssh attribute, which allows this
resource to be used to generate temporary OpenSSH credentials, so that
e.g. a Terraform configuration could generate its own keypair to use
with the aws_key_pair resource. This has the same caveats as all cases
where we generate private keys in Terraform, but could be useful for
temporary/throwaway environments where the state either doesn't live for
long or is stored securely.
This builds on work started by Simarpreet Singh in #4441 .
As of this commit this provider has only logical resources that allow
the creation of private keys, self-signed certs and certificate requests.
These can be useful when creating other resources that use TLS
certificates, such as AWS Elastic Load Balancers.
Later it could grow to include support for real certificate provision from
CAs using the LetsEncrypt ACME protocol, once it is stable.
Martin Atkins