[Route Groups] Rename GroupRouteBuilder to RouteGroupBuilder

[halter73]

Background and Motivation

RouteGroupBuilder sounds better than GroupRouteBuilder. In the original API proposal (#36007) this was called RouteGroup which is closer to the name I am suggesting here. RouteGroup is also an alternative name that I think is better than GroupRouteBuilder. I proposed GroupRouteBuilder in the follow up comments because it better aligned with IEndpointRouteBuilder, but now I think that's unimportant.

Proposed API

namespace Microsoft.AspNetCore.Routing;

- public sealed class GroupRouteBuilder : IEndpointRouteBuilder, IEndpointConventionBuilder
+ public sealed class RouteGroupBuilder : IEndpointRouteBuilder, IEndpointConventionBuilder

Usage Examples

Before

GroupRouteBuilder group = app.MapGroup("/todos");
group.MapGet("/", (int id, TodoDb db) => db.ToListAsync());

After

RouteGroupBuilder group = app.MapGroup("/todos");
group.MapGet("/", (int id, TodoDb db) => db.ToListAsync());

Alternative Designs

• Keep it as GroupRouteBuilder since that puts "Group" up front even if using "Group" as an adjective sound weird.
• Go with the ven shorter RouteGroup.

Risks

Low. It's only been released in preview4 and it would only break apps that reference the type name instead of just using var.

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[halter73]

API review notes:

1. Should we do this?
   This has only been out for a preview release. A lot of people use var. Now or never, and it seems slightly better.