Adding customProps to API

[geelen]

This lets a user add additional context per-request to their ApiHandler, by providing a customProps callback. The resulting object will be added to ctx.props.customProps:

new OAuthProvider({
  // ... other options ...
  customProps: async (request, env, ctx) => {
    // Will be added to ctx.props.customProps when invoking apiHandler
    return {
      customToken: request.headers.get('x-custom-token'),
      featureFlags: await env.FEATURES.parse(request.headers.get('x-feature-flags')),
    }
  }
})

This fixes #36

[kentonv]

Why is this needed? The ApiHandler receives the original request, so why can't it just read the headers directly?

[geelen]

Ah this is probably another case of the Agents + Oauth combo hiding where the fix needs to happen. Agents does this: https://github.com/cloudflare/agents/blob/main/packages/agents/src/mcp/index.ts#L608

await doStub._init(ctx.props);

So anything you add to ctx.props would have come right through. But yeah, potentially it's the McpAgent api that needs an API extension to allow converting headers to props instead, if it's already getting the raw request?

[kentonv]

Yes, that seems right to me -- this should be pushed up to the agents layer.

Though my opinion: I would find a way to separate this from ctx.props entirely. Maybe add a new parameter for "request info". ctx.props is meant to be info about the connection / grant / capability that the client exercised, not information about the request.