* Refactoring openssh_keypair for multiple backends
* Fixing cryptography backend validations
* Simplifying conditionals and excess variable assignments
* Fixing docs and adding cleanup for integration tests
* Fixing docs and public key validation bugs in crypto backend
* Enhancing cryptogagraphy utils to raise OpenSSHErrors when file not found
* Adding missed copyright and cleanup for idempotency test keys
* Fixing doc style
* Readding crypto/openssh for backwards compatibility
* Adding changelog fragment and final simplifications of conditional statements
* Applied initial review suggestions
* Integrating openssh module utils with openssh_keypair
* Added explicit PEM formatting for OpenSSH < 7.8
* Adding changelog fragment
* Adding OpenSSL/cryptography dependency for integration tests
* Adding private_key_format option and removing forced cryptography update for CI
* Fixed version check for bcrypt and key_format option name
* Setting no_log=False for private_key_format
* Docs correction and simplification of control flow for private_key_format
* Adding openssh utils and unit tests
* Adding changelog fragment and correcting RSA default size
* Adding changelog fragment
* Added passphrase update, test cases, and check for SSH private key loader
* corrected ecdsa type when loading
* Resolving inital review comments
* Fixed import in unit tests
* Cleaning up validation functions
* Separating private/public key related errors; Adding verify method
* Expressed generate/load functions as classmethods and cleaned up method comments
* Added support for loading asymmetric key pairs of PEM and DER formats
* Refactored loading/generation for Asym keypairs into classmethods
* Rescoped helper functions and classmethods for OpenSSH Keypair
* Corrected docstring for OpenSSH_Keypair.generate()
* Fixed import errors for sanity tests
* Improvements to comparison, key verification, and password validation
* Added comparison tests, simplified password validation, fixed Ed25519 load bug
* Adding additional equivalence tests with passphrases
