Implement New Content Creation Flow in Relationship Field

[oidacra]

Parent Issue

#30495

User Story

As a content editor, I want to create new content directly from the Relationship Field and have it automatically related to my current content.

Acceptance Criteria

1. Sidebar Implementation

   • Create new content sidebar
   • Implement back button navigation
   • Add proper form loading
   • Handle form submission
   • Show loading states
   • Implement proper error handling

2. Content Creation Flow

   • Open sidebar with empty contentlet
   • Support all content types
   • Validate before saving
   • Auto-select created content
   • Close sidebar after successful save
   • Show error messages on failure

3. UX Requirements

   • Smooth sidebar transitions
   • Clear loading indicators
   • Proper form validation feedback
   • Confirmation messages
   • Back button warning if unsaved changes

Proposed Objective

Technical User Experience

Proposed Priority

Priority 2 - Important

[github-actions[bot]]

PRs:

• https://github.com/dotCMS/core/pull/32424

[hmoreras]

Note to QA:

• This cover the scenario for the new edit content and not for the legacy edit content (will be worked in other card )

https://github.com/user-attachments/assets/cf47a9f6-bfce-47d6-9da6-870126ea9025

[nicobytes]

This card has passed QA 🎉

https://github.com/user-attachments/assets/29ee0a65-b302-4425-88d9-bd3ceae3f61e