Adding command 'ai:models:attach'

[sbosio]

Description

This PR implements the ai:models:attach command with tests according to the design outlined in the UX design doc.

How to test

Prepare your environment for testing

• Fetch this branch.
• Run yarn && yarn build.
• Set the HEROKU_INFERENCE_ADDON to the production canary add-on via export HEROKU_INFERENCE_ADDON="inference-staging"

Actual testing

• Verify that help looks ok: ./bin/run ai:models:attach --help
• Create a test app: heroku apps:create test-cli-plugin-ai
• Run ./bin/run ai:models:create claude-3-haiku -a test-cli-plugin-ai --as HAIKU_ORIGINAL to create a provisioned model.
• Run heroku addons -a test-cli-plugin-ai and grab the add-on name for the provisioned model.
• Run ./bin/run ai:models:attach <addon-name> -a test-cli-plugin-ai --as HAIKU_AGAIN and confirm that the command succeeds, creating another attachment to the model resource. Use heroku config -a test-cli-plugin-ai to confirm that config vars HAIKU_AGAIN_... share the exact same values as HAIKU_ORIGINAL_....
• Run ./bin/run ai:models:create claude-3-haiku -a test-cli-plugin-ai --as HAIKU_AGAIN to create a new provisioned model reusing the attachment name. A confirmation step will be required to allow overwriting the config vars. Confirm by entering the app name and confirm that now HAIKU_ORIGINAL_KEY and HAIKU_AGAIN_KEY have different values.
• Remove your test app to get rid of all add-ons: heroku apps:destroy -a test-cli-plugin-ai

SOC2 Compliance

GUS Work Item

[k80bowman]

Works great! Just one suggestion, but it's not blocking.