Add example/javaweb/4-hello-micronaut and 5-todo-micronaut

[lihaoyi]

It's pretty minimal, but it's a start. Apart from Spring/Spring-Boot, Micronaut and Quarkus seemed like the next most popular Java web frameworks according to the Jetbrains Developer Survey https://www.jetbrains.com/lp/devecosystem-2023/java/, and I found the Micronaut examples more plentiful than the Quarkus examples

hello-micronaut is a minimal example, while todo-micronaut exercises many more components parts of micronaut at least once: database access, routing, JSON serialization, static files, JS/CSS, etc.

One big thing we are missing integration of Micronaut's AOT support. That can come in a follow up, either by me or by someone else who's able to contribute it

[lefou]

Should we welcome the reader to create and add a micronaut contrib module with more functionality?

[lihaoyi]

I think as far as the doc-site, it is concerned it's best to leave it as an example. I can open a ticket/bounty later to formalize MicronautModule as a contrib/ module and link it from the docs

[lefou]

I was more thinking of encouraging them to contribute. Just to show them, we are open for adding support and convenience once there is demand/contribution. I haven't any idea how widely used micronaut is and if there is any demand in a dedicated plugin?

[lihaoyi]

We'll have to see; the demand in the past is zero because we didn't target Java developers, but going forward there may be demand.

Given the nascent nature of these examples, let's leave MicronautModule as an example code snippet for now, and we can see if there is anyone willing to contribute fleshing it out and maintaining it as an official contrib/ module.