Add ability to accept more than one child in <Reference> Fields

[fzaninotto]

Problem

Developers often need to render more than one field of the reference table (e.g. if the users table has a first_name and a last_name field) in a <ReferenceField>. And <FunctionField> is a bit cumbersome.

Solution

Let <ReferenceField> accept more than one child, so that developers can use as many <Field> as they like:

import { Show, SimpleShowLayout, ReferenceField, TextField, DateField, FunctionField } from 'react-admin';

export const PostShow = () => (
    <Show>
        <SimpleShowLayout>
            <TextField source="id" />
            <TextField source="title" />
            <DateField source="published_at" />
            <ReferenceField label="Author" source="user_id" reference="users">
                <TextField source="first_name" />{' '}
                <TextField source="last_name" />
            </ReferenceField>
        </SimpleShowLayout>
    </Show>
);

• <ReferenceField> code, doc and tests
• <ReferenceManyField> code, doc and tests
• <ReferenceOneField> code, doc and tests
• <ReferenceArrayField> code, doc and tests

[slax57]

Otherwise, that's great! And we can probably do the same with ReferenceManyField too

[slax57]

Build is failing though 🙁

[fzaninotto]

It was a GitHub failure. I relaunched the build and it passes.

[fzaninotto]

Back to WIP to address other reference field components

[fzaninotto]

back to RFR

[djhi]

💯