feat(data-modeling): add nested field to object in diagram COMPASS-9742

[Anemy]

COMPASS-9742

Old pr #7300
I'll do the e2e tests in a separate pr as they are testing more field interactions than just this.

[Copilot]

Pull Request Overview

This PR adds functionality to insert nested fields into object fields within data modeling diagrams, enabling users to add fields directly to object-type fields rather than only at the top level of collections.

• Extends getNewUnusedFieldName to support nested field paths for generating unique field names within object fields
• Adds onAddNestedField action to create nested fields at specified parent paths
• Updates diagram component to handle nested field addition through new callback handlers

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

File	Description
packages/compass-data-modeling/src/utils/schema.ts	Extended getNewUnusedFieldName to traverse nested field paths
packages/compass-data-modeling/src/utils/nodes-and-edges.ts	Added getBaseFieldsFromSchema function and refactored field creation logic
packages/compass-data-modeling/src/store/diagram.ts	Added onAddNestedField action to handle nested field creation
packages/compass-data-modeling/src/components/diagram-editor.tsx	Connected nested field addition functionality to UI callbacks

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[nbbeeken]

A nothing comment but I feel compelled to suggest, why aren't we using "_" instead of "-" since I feel like snake case is the typical format for document keys. But that's just my onion 🧅 (smelly opinion)

[Anemy]

No reason. I think we just did it that way, I'm cool with either, if there's a standard for it let's do it that way! I'll include that change in another pr to avoid another ci run here.