Extension point: custom add-resource dialog

[hpehl]

Parent: #320

Summary

Allow resources to replace the generic metadata-driven add dialog with a resource-specific wizard or custom dialog. Currently, AddResourceDialogs auto-generates form items from the :add operation's parameter descriptions with no way to customize the dialog.

Motivation

The classic example is a multi-step datasource wizard that walks the user through connection settings, pool configuration, validation, and timeouts — instead of presenting all parameters in a single flat form. Similar use cases exist for:

• Security domains (multi-step authentication/authorization setup)
• Credential stores (key store selection + alias configuration)
• Messaging destinations (topic/queue with specific defaults)
• Any resource where the generic form doesn't provide enough guidance or where parameters have complex interdependencies

Capabilities

• Replace the add dialog entirely — provide a custom Promise<ModelNode> factory that replaces DialogBricks.addResourceModal()
• The custom dialog receives the same inputs (parent template, child name, singleton flag) and returns the same Promise<ModelNode> result

Registration

A registry keyed by Environment + AddressTemplate. When DialogBricks.addResourceModal() is called for a matching template, the registry delegates to the custom dialog factory instead.

Affected Call Sites

• ModelBrowser.add() — model browser add button
• FinderBricks — finder column add action
• ResourceList — resource list add button
• CapabilityReferenceSupport / PathSupport — inline "create new" from form fields

Open Questions

• Should the custom dialog factory also handle the wizard variant (addResourceWizard) for multi-template scenarios?
• Should there be a base class that provides common wizard infrastructure (step navigation, validation, progress) that custom wizards can extend?