Auto-detection for Hilla's endpoints

[mshabarov]

Describe your motivation

Vaadin Flow adds endpoints generation Node Tasks (see NodeTasks::addEndpointServicesTasks) if Hilla's views are present and base Hilla class is in class path.
This, however, doesn't take into account a presence of endpoint classes marked by AtEndpoint or AtBrowserCallable, which leads to wrong detection and not generating the endpoints in the end.

Describe the solution you'd like

Vaadin Flow can check:

• the presence and content of a frontend/generated/openapi.json file (if this file exists at the point where we need to take a decision in Flow about starting the generator), specifically the "tags" json array.
• presence of any AtEndpoint or AtBrowserCallable annotations in the project.

Additional context

Vaadin 24.4.

[mcollovati]

Can we also prevent running TaskGenerateEndpoint if there are no endpoint annotated classes? (I mean when potential Hilla views are detected, but there are no endpoint implementations)

[mshabarov]

Yeah, it would be reasonable to skip it. Let's also check if skipping it has any side effects.