(DOCSP-39528): Consolidate User Metadata page

[dacharyc]

Pull Request Info - SDK Docs Consolidation

Jira ticket: https://jira.mongodb.org/browse/DOCSP-39528

Staged Page

• User Metadata

Page Source

Add links to every SDK's pages where you got the SDK-specific information:

• Flutter: User Metadata
• Kotlin: Manage User Metadata
• .NET: User Metadata
• Node.js: User Metadata
• Swift: User Metadata

PR Author Checklist

Before requesting a review for your PR, please check these items:

• [x] Open the PR against the feature-consolidated-sdk-docs branch instead of master
• [x] Tag the consolidated page for:
  • genre
  • meta.keywords
  • meta.description

Naming

• [x] Update Realm naming and the language around persistence layer/local/device per this document
• [x] Include .rst files comply with the naming guidelines

Links and Refs

• [x] Create new consolidated SDK ref targets starting with "_sdks-" for relevant sections
• [x] Remove or update any SDK-specific refs to use the new consolidated SDK ref targets
• [x] Update any Kotlin API links to use the new Kotlin SDK roles

Content

• [x] Shared code boxes have snippets or placeholders for all 9 languages
• [x] API description sections have API details or a generic placeholder for all 9 languages
• [x] Check related pages for relevant content to include
• [x] Create a ticket for missing examples in each relevant SDK: Consolidation Gaps epic

Reviewer Checklist

As a reviewer, please check these items:

• [ ] Shared code example boxes contain language-specific snippets or placeholders for every language
• [ ] API reference details contain working API reference links or generic content
• [ ] Realm naming/language has been updated
• [ ] All relevant content from individual SDK pages is present on the consolidated page