[release/7.0-preview4] Add MapGroup

[github-actions]

Backport of #41265 to release/7.0-preview4

/cc @halter73

Add MapGroup

Add a new MapGroup() extension method to IEndpointRouteBuilder.

Description

This returns a new builder for defining groups of endpoints with a common prefix that implements both the IEndpointRouteBuilder and IEndpointConventionBuilder interfaces. This can be used to add endpoints with the given group prefix, and to customize those endpoints using conventions.

Sample Usage

var app = WebApplication.Create(args);

var group = app.MapGroup("/todos");
group.MapGet("/", (int id, TodoDb db) => db.ToListAsync());
group.MapGet("/{id}", (int id, TodoDb db) => db.GetAsync(id));
group.MapPost("/", (Todo todo, TodoDb db) => db.AddAsync(todo));

var nestedGroup = group.MapGroup("/{org}");
nestedGroup.MapGet("/", (string org, TodoDb db) => db.Filter(todo => todo.Org == org).ToListAsync());
nestedGroup.RequireCors("AllowAll");

// This applies to all endpoints defined on group and nestedGroup
group.RequireAuthorization();

// ...

Fixes #36007

Customer Impact

This is a new highly requested feature that makes organizing groups of endpoints easier and less repetitve.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

This is a new API. The change to existing code is very small and non-impactful unless the new MapGroup method is called.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

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[Pilchie]

This was approved over email.