consistent context overrides (redirect)

[ssube]

Multiple services need to override parts of an outgoing command or message's context:

• the completion controller has a defaultTarget
• the echo controller has a defaultTarget and forceChannel
• the base generator has a defaultContext and defaultTarget
• the express listener has a defaultTarget
• the loopback listener has a defaultTarget and needs a forceChannel

Many of these implement the same new Context({...defaults, ...options, ...force}) structure.

Extract that into a helper that will provide defaults and overrides to a Context. It needs to set the:

• channel: ChannelData (id and thread)
• name: string (user display name)
• source: source: boolean | service: ServiceMetadata (default: source: true)
• target: source: boolean | service: ServiceMetadata (default: source: true)
• user: User (which sets name and uid)

Scope

• add ContextRedirect interface
• add redirectContext(...): Context helper
  • Context, ContextRedirect args: from incoming entity and config
  • services: ServiceModule, source: Listener = undefined args: service module for source/target metadata lookups, source for source = true redirects
• ensure name/uid is set
• look up User from uid? would be async
• refactor existing services
• update example config
• fix tests
• update docs
• add new interfaces to schema