Add support for decoration in base field handling

[enderahmetyurt]

Description

This PR introduces a new decorate option for field definitions, allowing developers to format the display output only (e.g., in Show and Index views) without affecting the edit forms.

Previously, this was only achievable using the format_using option, which applies formatting to both display and edit contexts.

This improves code clarity and developer experience by removing unnecessary conditional logic and making the intent more explicit.

Why this is useful:

• Simplifies display-only customization.
• Keeps form input behavior untouched.
• Makes field declarations cleaner and easier to reason about.

#3728

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[codeclimate]

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[Paul-Bob]

Hey @enderahmetyurt, this is looking great, thanks a lot for submitting this contribution!

I've just pushed a few small tweaks.

Once we have a test and some documentation in place, this should be good to go. Would you be able to pick those up?

Really appreciate your work on this

[enderahmetyurt]

Cheers @Paul-Bob it was fun ❤️

Once we have a test and some documentation in place, this should be good to go. Would you be able to pick those up? I can do whatever we need. Do I need to write some tests and documentation?

[Paul-Bob]

Yes, @enderahmetyurt

Including documentation and tests in each PR is essential. It ensures others are aware of the option and helps guarantee it continues to behave as expected with future changes.

[adrianthedev]

Do we need the || nil? I thought they defaulted to nil.

[Paul-Bob]

{}[:autocomplete] already returns nil

That is, accessing a non-existent key in a hash yields nil by default.
So if args doesn't contain :autocomplete, then args[:autocomplete] is already nil.
The expression args[:autocomplete] || nil is therefore equivalent to nil || nil, which is redundant.