Support for external keys and importing custom key material
Add support for external keys and importing custom key material (#21)
* Log X-Amz-Target if this cannot be handled
Makes it easier to know what method needs to be added in future
* Upgrade Go Modules
* Add support for EXTERNAL origin to be specified when creating key
* Implement GetParametersForImport
Just attach these to a key. Thus, we only ever have one active set of parameters per key.
* Implement ImportKeyMaterial
* Implement DeleteImportedKeyMaterial
* Update README
* Add support for seeding EXTERNAL keys