Add Conditionable trait to support ->when() and ->unless()

[ziming]

WHY

BEFORE - What was wrong? What was happening before this PR?

Nothing

AFTER - What is happening after this PR?

The Conditionable trait from laravel 8 is added. (Backpack minimum laravel 8 version is higher than when this is added into laravel so it is very safe)

https://www.amitmerchant.com/conditionally-executing-callbacks-conditionable-trait-laravel-8x/

I think this will greatly improve the fluent flexibility and reduce if () clauses as you can chain methods on a conditional basis in a fluent way.

HOW

How did you achieve that, in technical terms?

Add the Conditionable trait

Is it a breaking change?

No

How can we test the before & after?

Try chaining ->when() or ->unless() method and inside it call other fluent methods conditionally

Feel free to edit this PR and add the Conditionable trait to other classes too (filters, columns.etc), I can add it too if you all want but tell me which classes

I think this is a small change that is a big improvement to developer DX

[tabacitu]

I freaking LOVE this! Awesome idea @ziming .

@pxpm could you please take a look at it, this week or the next? After you free yourself of Dropzone, Uploaders, Media.

It's a really cool feature, I mean... this could be this months' 5.x feature, right?! Easy to do, significant impact.

My questions:

1. Where should we use this? I'm thinking Fluent Fields, Fluent Columns, Fluent Filters; am I missing something?

2. How do we document this?

Thanks @ziming !

[ziming]

Laravel's Macroable trait can be considered in another PR as well if it isn't done yet.

[tabacitu]

Laravel's Macroable trait can be considered in another PR as well if it isn't done yet.

✅ Already done 😉

[maurohmartinez]

Moving this here to continue it. Great idea @ziming... thanks!