Allow users to add custom secrets

[malhotra5]

What problem or use case are you trying to solve?

Users may have custom secrets and api keys they want Openhands to access; we should have some way to allow users to specify these values through the UI and store it in their settings.

Describe the UX of the solution you'd like

Add a section to the settings modal. User could add new entries with secret name and value.

Do you have thoughts on the technical implementation?

1. We should create a unified settings store for users

2. We already export $GITHUB_TOKEN in the remote runtime when we see the agent attempting to use $GITHUB_TOKEN. We would do something similar for other user secrets.

Describe alternatives you've considered

Additional context
cc @tofarr who may be working on this

[enyst]

This is an interesting topic. They're SANDBOX_ENV_* variables, a subset which is the secret category among those.

[jaybutera]

There's agents for reading and writing files. Would it make sense to have one for getting/storing secrets to a central secrets file?