Better defaults for the Show page

[timoschilling]

I'll turn this into a PR once there's code to go along with the idea.

This replaces the stale #1077.

# Renders the default table
show do
  attributes_table
end

# Removes specific attributes
show do
  attributes_table except: [:foo, :bar]
end

# Adds extra (virtual) attributes
show do
  attributes_table with: :baz
end

[timoschilling]

test will follow

[timoschilling]

We to do a banking change here.

The old attributes_table supports this:

attributes_table foo: 1, bar: 2

But this collides with the possibility to set options (:expect/:with).
This still works:

attributes_table [foo: 1, foo: 2]
attributes_table [{foo: 1, foo: 2}]

How should we deal with that?

[seanlinsley]

The object would always be the first element:

attributes_table foo: 1, bar: 2
attributes_table({foo: 1, bar: 2}, except: [:foo])

[seanlinsley]

It looks like this PR removes the ability to pass in a Hash, but as I said above, it's not necessary to drop that feature.

[varyonic]

I propose to close this as incomplete (insufficient tests) and abandoned. Sean thought it could be salvaged but Timo was not convinced. I looked at finishing this myself but the benefit is minor and I don't think it is worth it.

[Fivell]

@varyonic , agree