Ask for API base path while configuring OpenAI compatible custom provider

[ringods]

Describe the bug

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A clear and concise description of what the bug is.

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To Reproduce
Steps to reproduce the behavior:

1. Configure an OpenAPI compatible custom provider
2. Follow the wizard, where the host and an authentication key are asked
3. No base path is asked.

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Expected behavior
A clear and concise description of what you expected to happen.

On Scaleway, the base API URL is https://api.scaleway.ai/v1. User access to AI can also be scoped a specific Scaleway project:

https://www.scaleway.com/en/docs/generative-apis/api-cli/using-generative-apis/#projects

In such cases, the endpoint becomes of the form:

https://api.scaleway.ai/78e655b5-feb0-417c-bb3f-8c448bd0e8da/v1

where 78e655b5-feb0-417c-bb3f-8c448bd0e8da represents the Scaleway Project ID. If I want to configure the custom provider in goose, I want to set 78e655b5-feb0-417c-bb3f-8c448bd0e8da/v1 as the base path in the configuration wizard.

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Screenshots
If applicable, add screenshots to help explain your problem.

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Please provide the following information

• OS & Arch: macOS Tahoe 26.3
• Interface: CLI
• Version: 1.25.2
• Extensions enabled: None. I just installed goose and want to configure my first (custom) provider
• Provider & Model: None. I just installed goose and want to configure my first (custom) provider

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Additional context
Add any other context about the problem here.

[ringods]

goose 1.26.0 seems to ask for all the details correctly now. However, after filling them in, I get an authentication error now:

I use the exact same endpoint and credentials in the settings of my Jetbrains IDEs and there they work correctly, hence I doubt it is an authentication error. I would rather think there is another error but masked in the code path for the auth handling.

Jetbrains screenshot:

[suyunzzz]

same error