Sulu3.0 integration (clean up version)

[mamazu]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	fixes #issuenum
Related issues/PRs	#issuenum
License	MIT

What's in this PR?

Explain the contents of the PR.

Why?

Which problem does the PR fix? (remove this section if you linked an issue above)

Example Usage

// If you added new features, show examples of how to use them here
// (remove this section if not a new feature)

$foo = new Foo();

// Now we can do
$foo->doSomething();

BC Breaks/Deprecations

Describe BC breaks/deprecations here. (remove this section if not needed)

To Do

• Create documentation

[mamazu]

@alexander-schranz Since I have no idea how the new content structure works. Can you check out the last commit and see if that is the correct implementation?

[Prokyonn]

Why do we need the resourceKey here? I think we can omit this exception, as the resourceKey for the reference is always Form::RESOURCE_KEY

[mamazu]

From what I understand this is the type of content into which you're embedding the form (if it's an article, a snippet). Because the form needs to know how to get the title of the content it's being rendered on. (see implementation of the TitleProviderInterface

[Prokyonn]

I think we usually used resourceLoader without the key

[Prokyonn]

hmm this is a design break, as we should not use the repository in the property resolver.
But I don't think we have currently another way to adjust the view array

[Prokyonn]

Should be only FormResourceLoader the resourceloader is independent of the propertyresolver and therefore should be used for both single and multi selections.