feat: add available tools endpoint

[goetzrobin]

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There's currently no way to query the API for what tools can be added to an agent.

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Add an available-tools endpoint that takes in a agentId and returns all the tools that can be added to it

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We can fetch all tools and then compare them on the FE to filter out those the agent already has.
However, this does not work well with pagination.

Happy to discuss if this is the preferred approach though

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This issue has been automatically closed due to 60 days of inactivity.