.env.example has wrong keys for google

[theoephraim]

This docs page shows the correct keys for google/gemini are GOOGLE_GENERATIVE_AI_API_KEY or GEMINI_API_KEY

But the .env.example file includes a GOOGLE_API_KEY.

The example file should probably just include one (maybe OPENAI_API_KEY?) and then have a link to a docs page showing all the options.

Alternatively you could make it much more comprehensive and include them all, along with links - or you could ask the user during the create flow which provider they want to use.