fix: Manage empty props object

[taorepoara]

About this PR

When no props is defined an empty object is sent in the view and listener requests.

When a view handle a props struct as optional and view is called without props, the empty props object is sent and we have an error while parsing to the expected props struct.

To resolve this, if the props object is empty, we return None.

How to test my changes

Create a view that can have an optional props object:

use lenra_app::{
    components::lenra::text,
    props,
    view::{ViewParams, ViewResponse, ViewResponseGenerator},
    Result,
};
use serde::{Deserialize, Serialize};
use serde_json::Value;

#[derive(Serialize, Deserialize)]
pub struct TestProps {
    pub val: String,

props!(TestProps);

pub fn test(params: ViewParams<Value, TestProps>) -> Result<ViewResponse> {
    let val = if let Some(props) = params.props {
        props.val
    } else {
        "default value".into()
    };
    let result: LenraComponent = text(val).into();
    Ok(result.gen())
}

Define this view in two routes, one with the props and one without:

vec![
Route::builder()
      .path(format!("/test-props", path))
      .view(
          view("test").props(Some(
              TestProps {
                  val: "test value".into(),
              }
              .try_into()
              .unwrap(),
          )),
      )
      .try_into()
      .unwrap(),
Route::builder()
      .path(format!("/test-props", path))
      .view(view("test"))
      .try_into()
      .unwrap(),
]

Checklist

• I didn't over-scope my PR
• My PR title matches the commit convention
• I did not include breaking changes
• I made my own code-review before requesting one

I included unit tests that cover my changes

• 👍 yes
• 🙅 no, because they aren't needed
• 🙋 no, because I need help

I added/updated the documentation about my changes

• 📜 README.md
• 📕 docs/*.md
• 📓 docs.lenra.io
• 🙅 no documentation needed

[github-actions]

🎉 This PR is included in version 1.0.1 🎉

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