Add README with badges and docs

Author: stephanprobst

README.md

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-# Endpointer
+# Endpointer
+
+[![Build](https://github.com/stephanprobst/Endpointer/actions/workflows/build.yml/badge.svg)](https://github.com/stephanprobst/Endpointer/actions/workflows/build.yml)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![netstandard2.0](https://img.shields.io/badge/netstandard-2.0-blue)](https://docs.microsoft.com/en-us/dotnet/standard/net-standard)
+[![Roslyn](https://img.shields.io/badge/Roslyn-Source%20Generator-blueviolet)](https://docs.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/)
+
+A **C# source generator** for ASP.NET Core Minimal APIs implementing the **REPR (Request-Endpoint-Response) pattern**.
+
+Endpointer is a thin layer above ASP.NET Core - not a framework. It generates the boilerplate at compile time with no reflection, while you keep full control over your endpoints.
+
+## Features
+
+- **Zero runtime overhead** - All code is generated at compile time
+- **REPR pattern** - Clean separation with Request, Endpoint, and Response in one file
+- **Automatic DI registration** - Primary constructor parameters are auto-registered
+- **Automatic route mapping** - All endpoints discovered and mapped via source generation
+- **Native ASP.NET Core** - Uses `TypedResults`, `IEndpointRouteBuilder`, and standard middleware
+- **Incremental generator** - Fast builds with Roslyn's latest `IIncrementalGenerator` API
+- **No reflection** - Everything resolved at compile time
+
+## Quick Start
+
+### 1. Install the package
+
+```bash
+dotnet add package Endpointer
+```
+
+### 2. Create an endpoint
+
+```csharp
+using Microsoft.AspNetCore.Http.HttpResults;
+
+public class GetTimeEndpoint(TimeProvider timeProvider)
+{
+    public record GetTimeResponse(DateTimeOffset CurrentTime);
+
+    public class Endpoint : IEndpoint
+    {
+        public void MapEndpoint(IEndpointRouteBuilder endpoints)
+        {
+            endpoints.MapGet("/time", (GetTimeEndpoint ep) => ep.Handle());
+        }
+    }
+
+    public Ok<GetTimeResponse> Handle()
+    {
+        return TypedResults.Ok(new GetTimeResponse(timeProvider.GetUtcNow()));
+    }
+}
+```
+
+### 3. Register in Program.cs
+
+```csharp
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddEndpointer();  // Generated - registers all endpoint classes
+
+var app = builder.Build();
+
+app.MapEndpointer();  // Generated - maps all endpoints
+
+await app.RunAsync();
+```
+
+That's it! The source generator discovers all `IEndpoint` implementations and generates the registration code.
+
+## How It Works
+
+Endpointer uses Roslyn's incremental source generator to:
+
+1. **Discover endpoints** - Finds all nested classes implementing `IEndpoint`
+2. **Extract metadata** - Captures the outer class name and its primary constructor parameters
+3. **Generate registration** - Creates extension methods for DI and route mapping
+
+### Generated Code
+
+The generator produces two files:
+
+**IEndpoint.g.cs** - The marker interface:
+```csharp
+public interface IEndpoint
+{
+    void MapEndpoint(IEndpointRouteBuilder endpoints);
+}
+```
+
+**EndpointerRegistration.g.cs** - Extension methods:
+```csharp
+public static class EndpointerExtensions
+{
+    public static IServiceCollection AddEndpointer(this IServiceCollection services)
+    {
+        services.AddScoped<GetTimeEndpoint>();
+        services.AddScoped<GetUserEndpoint>();
+        services.AddScoped<CreateUserEndpoint>();
+        // ... all discovered endpoints
+        return services;
+    }
+
+    public static IEndpointRouteBuilder MapEndpointer(this IEndpointRouteBuilder endpoints)
+    {
+        new GetTimeEndpoint.Endpoint().MapEndpoint(endpoints);
+        new GetUserEndpoint.Endpoint().MapEndpoint(endpoints);
+        new CreateUserEndpoint.Endpoint().MapEndpoint(endpoints);
+        // ... all discovered endpoints
+        return endpoints;
+    }
+}
+```
+
+## The REPR Pattern
+
+REPR (Request-Endpoint-Response) organizes API code by feature rather than by layer:
+
+```
+Endpoints/
+├── Users/
+│   ├── CreateUserEndpoint.cs    # POST /users
+│   ├── GetUserEndpoint.cs       # GET /users/{id}
+│   ├── UpdateUserEndpoint.cs    # PUT /users/{id}
+│   └── DeleteUserEndpoint.cs    # DELETE /users/{id}
+└── Health/
+    └── HealthEndpoint.cs        # GET /health
+```
+
+Each file contains:
+- **Request** - Input DTOs (records)
+- **Endpoint** - Route mapping (nested `IEndpoint` class)
+- **Response** - Output DTOs (records)
+- **Handler** - Business logic (methods on outer class)
+
+## Requirements
+
+- **.NET 10.0** or later (for the application)
+- The generator itself targets **netstandard2.0** for broad compatibility
+
+## Building
+
+```bash
+# Build
+dotnet build src/Endpointer.slnx
+
+# Test
+dotnet test --solution src/Endpointer.slnx
+```
+
+## License
+
+This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.