feat: add initial implementation of osiris, the TLS terminator for Anubis

Signed-off-by: Xe Iaso <me@xeiaso.net>

cmd/osiris/internal/entrypoint/entrypoint.go

@@ -0,0 +1,37 @@
+package entrypoint
+
+import (
+	"fmt"
+	"log/slog"
+	"net/http"
+
+	"github.com/TecharoHQ/anubis/cmd/osiris/internal/config"
+	"github.com/TecharoHQ/anubis/internal"
+	"github.com/hashicorp/hcl/v2/hclsimple"
+	healthv1 "google.golang.org/grpc/health/grpc_health_v1"
+)
+
+type Options struct {
+	ConfigFname string
+}
+
+func Main(opts Options) error {
+	internal.SetHealth("osiris", healthv1.HealthCheckResponse_NOT_SERVING)
+
+	var cfg config.Toplevel
+	if err := hclsimple.DecodeFile(opts.ConfigFname, nil, &cfg); err != nil {
+		return fmt.Errorf("can't read configuration file %s:\n\n%w", opts.ConfigFname, err)
+	}
+
+	if err := cfg.Valid(); err != nil {
+		return fmt.Errorf("configuration file %s is invalid:\n\n%w", opts.ConfigFname, err)
+	}
+
+	rtr, err := NewRouter(cfg)
+	if err != nil {
+		return err
+	}
+
+	slog.Info("listening on", "http", cfg.Bind.HTTP)
+	return http.ListenAndServe(cfg.Bind.HTTP, rtr)
+}