feat(webapps): add login plugin point

[tasso94]

related to #3412

[danielkelemen]

Looks good to me.

• 👍 I like the simplicity. Also the example and how it demonstrates a simple use-case.
• 💬 It would be nice if based on the result the plugins could be re-rendered instead of hiding and displaying elements from the data plugin. What do you think? I feel like it's better if the plugin controls itself.

[tasso94]

💬 It would be nice if based on the result the plugins could be re-rendered instead of hiding and displaying elements from the data plugin. What do you think? I feel like it's better if the plugin controls itself.

Thanks for raising this.

I think that the solution, while sounding attractive at first glance, has disadvantages compared to the approach I've chosen:

• Data plugin points can be used for all other render plugin points and are not strictly bound to just one.
• When initially loading the render plugin point, we would have to synchronize it with the HTTP request, which leads to delays and may only be necessary in some cases (not for all use cases).
• Unconditional re-rendering bound to the HTTP request is inefficient and might not be desired for every use case.
• When a render plugin needs to consume data from multiple (possibly unrelated) sources, the result of all requests needs to be awaited before the plugin point can be rendered.