Implement Multi-Process Handling (#7)

Refactor code to support starting of multiple back end llama.cpp servers. This functionality is exposed as `profiles` to create a simple configuration format. 

Changes: 

* refactor proxy tests to get ready for multi-process support
* update proxy/ProxyManager to support multiple processes (#7)
* Add support for Groups in configuration
* improve handling of Model alias configs
* implement multi-model swapping
* improve code clarity for swapModel
* improve docs, rename groups to profiles in config

proxy/helpers_test.go

@@ -0,0 +1,58 @@
+package proxy
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sync"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+var (
+	nextTestPort int = 12000
+	portMutex    sync.Mutex
+)
+
+// Check if the binary exists
+func TestMain(m *testing.M) {
+	binaryPath := getSimpleResponderPath()
+	if _, err := os.Stat(binaryPath); os.IsNotExist(err) {
+		fmt.Printf("simple-responder not found at %s, did you `make simple-responder`?\n", binaryPath)
+		os.Exit(1)
+	}
+
+	gin.SetMode(gin.TestMode)
+
+	m.Run()
+}
+
+// Helper function to get the binary path
+func getSimpleResponderPath() string {
+	goos := runtime.GOOS
+	goarch := runtime.GOARCH
+	return filepath.Join("..", "build", fmt.Sprintf("simple-responder_%s_%s", goos, goarch))
+}
+
+func getTestSimpleResponderConfig(expectedMessage string) ModelConfig {
+	portMutex.Lock()
+	defer portMutex.Unlock()
+
+	port := nextTestPort
+	nextTestPort++
+
+	return getTestSimpleResponderConfigPort(expectedMessage, port)
+}
+
+func getTestSimpleResponderConfigPort(expectedMessage string, port int) ModelConfig {
+	binaryPath := getSimpleResponderPath()
+
+	// Create a process configuration
+	return ModelConfig{
+		Cmd:           fmt.Sprintf("%s --port %d --respond '%s'", binaryPath, port, expectedMessage),
+		Proxy:         fmt.Sprintf("http://127.0.0.1:%d", port),
+		CheckEndpoint: "/health",
+	}
+}