Use migration ID as scaffolded migration type name

[Copilot]

• Modify MigrationsScaffolder.ScaffoldMigration to use migration ID as the type name
• Add test in MigrationsScaffolderTest to verify the type name in scaffolded code
• Fix OperationExecutorTest expected code templates to use migration ID-based type name
• Fix HierarchyId MigrationTests expected code templates to use migration ID-based type name
• Run all migration tests to verify no other failures (300/300 pass, 1215/1216 design tests pass — sole failure is unrelated SQL Server connectivity)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Append timestamp to scaffolded migration type names</issue_title>
<issue_description>When a new migration is added, EF currently scaffolds a .NET type with the name of the migration. This leads to a variety of issues around the name being problematic in C#:

• The type name happens to be the same as a .NET type. A very frequent case is when users do dotnet ef migrations add DateTime.
• The C# compiler now raises warnings when a type name could conflict with a future keyword (i.e. all-lowercase name), see #35938.

Migration files already have their creation timestamp prefixed to the name, so that migrations are properly sorted on the filesystem. We can simply append the same timestamp to the type name inside: public class DateTime_20250512080000 {...}.</issue_description>

Comments on the Issue (you are @copilot in this section)

@roji Tentatively proposing as a stretch goal in 10.

• Fixes Append timestamp to scaffolded migration type names #36066

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[Copilot]

Pull request overview

Updates migration scaffolding to avoid generated migration type names colliding with BCL types / triggering compiler warnings by appending the migration timestamp (already present in the migration ID / file name) to the generated class name.

Changes:

• Derive migrationTypeName by appending the timestamp portion of migrationId and pass it to GenerateMigration/GenerateMetadata.
• Add a design-time test asserting the timestamped type name appears in both the migration and metadata output.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/EFCore.Design/Migrations/Design/MigrationsScaffolder.cs	Appends migration ID timestamp to the generated migration type name when scaffolding.
test/EFCore.Design.Tests/Migrations/Design/MigrationScaffolderTest.cs	Adds test coverage ensuring generated code contains the timestamped type name and the original [Migration] attribute.

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[AndriySvyryd]

@ErikEJ FYI

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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