Minor improvements

[philipp-meier]

First of all, thank you for this plugin! I tried it with Zitadel and it just worked right away.

I made some minor improvements (in my opinion), while experimenting with the plugin:

• Added log levels to simplify the log function.
• Removed unnecessary initializers (rsaKeys, ecdsaKeys).
• Fixed a log message typo.
• Removed an unused parameter of exchangeAuthCode.
• Added error handling for "WriteString" (sha2, codeVerifier)
• Renamed the "aes" variables to "aesCipher" so that they do not collide with the aes package name anymore.

Maybe you find some of those changes useful.

BR Philipp