Fully support `Text#language`

[nikku]

What should we do?

• Incorporate schema validation for Text#language
• Document language feature

Why should we do it?

Ensure #858 is available to a wider audience, but also to potentially support JSON editors and graphql editors.

[christian-konrad]

@nikku my input here (from past issues):

• https://github.com/camunda/product-hub/issues/784#issuecomment-1364502317
  

• https://github.com/camunda/product-hub/issues/614#issuecomment-1416079794

[nikku]

@christian-konrad I believe we incorporated your input (cf. #858 (comment)).

The first iteration is a minimal one.

#871 tracks adding support for custom editors. As sketched the plan is not to add arbitrary editors to the core, but provide an extension point that folks can use to to hook up specific editors for any language.

[christian-konrad]

provide an extension point that folks can use to to hook up specific editors for any language.

Which folks?

[nikku]

Anyone, i.e. community members, or Camunda. On the Desktop and Web modeler side we need to decide which languages we support through actual editors.

But to make it clear: We are discussing GraphQL and Groovy today, we may discuss SQL, C#, JavaScript, EL expressions, and XML tomorrow. At the core we can build the foundations to plug in such editors, we cannot necessarily build all these editors ourselves.