plugins/aiven: add plugin for aiven-client

[staaldraad]

Overview

Adds support for the aiven-client (avn) for https://aiven.io

Type of change

• Created a new plugin
• Improved an existing plugin
• Fixed a bug in an existing plugin
• Improved contributor utilities or experience

Related Issue(s)

How To Test

• avn user login to generate an ~/.config/aiven/aiven-credentials.json file if you don't have an existing one
• avn user info
• init the plugin
• remove ~/.config/aiven/aiven-credentials.json
• avn user info
  • compare and see that the user info is the same as before using the plugin

Changelog

Authenticate the Aiven-Client CLI using Touch ID and other unlock options with 1Password Shell Plugins.