Simplify API-building experience without controllers

[mkArtakMSFT]

• Make it possible to move code as is from Ability to copy code from an endpoint handler to a controller (MapAction)
  • MapAction MVP (Implement a minimal version of MapAction  #29684)
  • Add new "MapAction" overloads (Add new "MapAction" overloads #30448)
  • MapAction Benchmarks (Add benchmarks for MapAction #29915)
• Move model-binding out of MVC
• Enable a model of use only what you need
• Ship controllers in libraries (out-of-scope)
• try to get middleware-like perf with MVC actions (out-of-scope)

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[halter73]

Next steps:

1. Prototype a non-source-gen version of MapAction (see source-gen version in uController). Runtime-generation (expression trees allowed). This could avoid intellisense/overload resolution issues the source-gen version has to deal with.

2. Design what a possible reflection API for lambda attributes might look like. See the houdini meeting notes.

Endpoints.MapPost("/api/todos/{id}", [Authorize] async (HttpContext http, TodoDbContext db, [FromBody] Todo inputTodo) =>
{
    var todo = await db.Todos.FindAsync(inputTodo.Id);
    if (todo == null)
    {
        http.Response.StatusCode = 404;
        return;
    }

    todo.IsComplete = inputTodo.IsComplete;
    await db.SaveChangesAsync();
    http.Response.StatusCode = 204;
});

[rcollette]

To me EndPoints.MapPost looks like a Route attribute turned into a method that takes an action as a parameter.

I'm not sure what the value in that is, but happy to be schooled.