Spike: Mount LB3 app and include its REST API in OpenAPI spec

[bajtos]

In this spike, we should investigate how to add an entire LB3 application into an LB4 project in such way that LB3 app's REST API is included in OpenAPI spec provided by the LB4 application and thus can be picked by LB4 clients including REST API Explorer.

#2274 (comment) by
@raymondfeng

In addition to the compat layer, should we evaluate the possibility to compose an existing LB3 app into LB4 with API explorer visibility?

#2274 (comment) by @richardpringle

I'm wondering if it's not easier to require an lb3 app in it's entirety as a dependency and boot the apps together.

[bajtos]

PoC pull request: #2318

I have created the following follow-up issues and closing this spike as done.

• Mount Express router with OpenAPI spec Mount Express router with OpenAPI spec #2389
• Docs: request-handling pipeline Docs: request-handling pipeline #2390
• Boot and mount LB3 app Boot and mount LB3 app #2391
• Example: mount LB3 app in LB4 Example: mount LB3 app in LB4 #2392
• Migration guide: mount LB3 in LB4 Migration guide: mount LB3 in LB4 #2393
• Spike: dynamically updated LB3 API (routes + spec) Spike: dynamically updated LB3 API (routes + spec) #2394