feat(js): propagate context to sub actions, expose context in prompts

[pavelgj]

Allows:

definePrompt({
  prompt: 'hello {{@auth.email}}',
})

Also changed express plugin to put auth into context.auth instead of just context.

[mbleigh]

I was thinking that GenerateOptions should actually have a context option so that context can be passed directly without needing to be embedding in a flow...WDYT?

[pavelgj]

I was thinking that GenerateOptions should actually have a context option so that context can be passed directly without needing to be embedding in a flow...WDYT?

Good idea. Done.