Bug

Fixes: NuGet/Home#14234
Fixes: NuGet/Home#13355
Fixes: NuGet/Home#13150
Fixes: NuGet/Home#13115
Fixes: NuGet/Home#13520
Fixes: https://github.com/NuGet/Client.Engineering/issues/2426
Fixes: https://github.com/NuGet/Client.Engineering/issues/1944

Description

Onboards the Package Source Mapping page to Unified Settings.

• New functionality: Editing an existing Package Source Mapping is now supported.
• F1 Help link now appears as a ? beside the page title
• Existing legacy options logic has been tucked away into a PackageSourceMappingUtility.
• The unit test SetValueAsync_PreviousMappingsToNonexistantSources_AddNewMapping_ExistingMappingsAreUnchangedAsync is important as it highlights the behavior of VS not deleting any misconfigured Package Source Mappings.
  We may want to revisit this behavior, but I didn't want to change that as part of the onboarding. It could be something customers are relying on today.

Side-effects

• Remove All command is not available at this time because the behavior of USX is an immediate action, which may result in customers accidentally permanently deleting all source mappings with 1 click. Telemetry shows this command was used very little in Legacy Options compared to add/remove commands.

• "Configure" link from PM UI Details Pane no longer auto-selects the Source Mapping for the selected package. USX doesn't yet support this functionality.

Related bugs (not being addressed)

These bugs will not be fixed, but they will have a change in behavior:

• [Bug Bash] Newly added package source mapping shouldn’t be case-sensitive in “Option->NuGet Package Manager->Package Source Mapping” window Home#13210

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.