[Feature request]Add ReadOnlyBindableReactiveProperty

[runceel]

@neuecc Are there any plans to introduce a read-only option for BindableReactiveProperty?
Related: runceel/ReactiveProperty#487 (comment)

This request was made in the GitHub issue mentioned above. In my opinion, this feature would be beneficial if added to the core of R3, so I documented it in this issue.

[neuecc]

I agree.
It seems better to have complex things like SubscriptionNode management standardized within R3.
I'd like to implement this!
Once it's completed, I'll likely request a review.

[neuecc]

It was difficult to prepare a ReadOnlyBindableReactiveProperty as an alternative implementation of a BindableReactiveProperty.
in v1.2.1, creating an interface IReadOnlyBindableReactiveProperty, but I wonder if that will be okay?
This is not a generic type, but just an object Value {get;}, so it's just an interface for exposing it in XAML.

To be honest, I would be happier if people just used BindableReactiveProperty as it is, ignoring the fact that it is mutable.

[runceel]

@neuecc Thank you. I have reviewed it and it works fine for XAML (I checked both WPF and WinUI3). However, while it serves well as an interface for XAML, I believe having generic versions would be beneficial for other use cases. Therefore, are there any technical blockers preventing the addition of generic interfaces such as IReadOnlyBindableReactiveProperty<T> and IBindableReactiveProperty<T>?

[neuecc]

@runceel
I thought there was a problem with the interface, so I only used non-generic types, but it was all in my head.
I added a generic version in #240.
I also added EnableValidation to the interface, as I thought it would be possible to enable validation without any problems.
If it looks okay, I'll release it, but what do you think?

[runceel]

@neuecc
Thank you! I have reviewed it, and it looks good. However, the binding system of WPF is reflection-based, so even when using IReadOnlyBindableReactiveProperty<T>, TwoWay binding works.
WinUI 3 uses a code generation-based binding system, so this implementation works fine.

In my opinion, creating a custom implementation for the read-only option would cover all cases, but the current implementation strikes a good balance between functionality and cost.

[neuecc]

Thank you for reviewing.
I also tried to completely Hide it by wrapping, but due to event propagation and other factors, it seems like it would cause unnecessary complications.
Since Observable<T> is an abstract class, IReadOnlyBindableReactiveProperty<T> cannot chain operators.
Therefore, I added AsObservable().
ac5974d
(Also, I realized that the return value of TおReadOnlyBindableReactiveProperty<T> wasn't IReadOnly in the first place...!)

[neuecc]

I've released in 1.2.3.