feat: migration providers whitelisting + documentation

[tnaum-ms]

This pull request introduces experimental features for the DocumentDB extension in VS Code, focusing on a new data migration framework and enhanced API safeguards. It also includes minor updates to documentation, localization strings, and code cleanup. Below is a summary of the most important changes grouped by theme.

Experimental Data Migration Framework

• Added documentation for a new experimental data migration feature, outlining its functionality, provider-based architecture, and preview phase restrictions. (docs/learn-more/data-migrations.md, docs/learn-more/data-migrations.mdR1-R92)
• Updated package.json to include a whitelist of registered clients allowed to use the experimental API. (package.json, package.jsonR922-R927)

API Safeguards and Validation

• Introduced a type guard (isValidPackageJson) to validate the DocumentDB API configuration in package.json and ensure calling extensions are whitelisted. (api/src/utils/getApi.ts, [1] [2]
• Enhanced authentication warnings with detailed instructions for users to expand the tree item of the selected cluster before proceeding. (src/commands/chooseDataMigrationExtension/chooseDataMigrationExtension.ts, [1] [2]

Documentation Updates

• Added a new section on data migrations to the documentation index and linked it in multiple places. (docs/index.md, [1]; docs/learn-more/index.md, [2]
• Updated example connection strings in the manual to use localhost instead of external clusters for clarity. (docs/manual/how-to-construct-url.md, docs/manual/how-to-construct-url.mdL87-R105)

Codebase Enhancements

• Refactored MigrationService to include methods for registering and unregistering migration providers, with automatic updates to VS Code context. (src/services/migrationServices.ts, [1] [2]
• Removed unused imports and commented out functionality related to adding new migration providers. (src/commands/chooseDataMigrationExtension/chooseDataMigrationExtension.ts, [1] [2] [3]

Localization Adjustments

• Updated localization strings for improved clarity, such as changing "Authentication is required for this action" to "Authentication is required to run this action." (l10n/bundle.l10n.json, [1] [2]

[Copilot]

Pull Request Overview

This PR introduces an experimental data migration framework for the DocumentDB extension along with enhanced API safeguards, documentation updates, and localization improvements.

• Refactored MigrationService to update VS Code context upon provider registration/unregistration.
• Updated the data migration command to improve authentication warnings and remove legacy code.
• Added a client whitelist to the API configuration in package.json and enhanced related documentation.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/services/migrationServices.ts	Refactored provider registration/unregistration and added context updates for migration providers.
src/commands/chooseDataMigrationExtension/chooseDataMigrationExtension.ts	Updated authentication prompts and commented out unused add-migration-provider code for clarity.
package.json	Included a whitelist of registered clients and updated the context condition for migration providers.
l10n/bundle.l10n.json	Updated localization strings to reflect new authentication warning details.
docs/manual/how-to-construct-url.md	Updated connection string examples to use localhost for clarity.
docs/learn-more/index.md & docs/learn-more/data-migrations.md	Added new sections documenting the experimental data migrations feature.
docs/index.md	Updated index to reference the new data migrations section.
api/src/utils/getApi.ts	Introduced a type guard to validate the API configuration and ensure calling extensions are whitelisted.