feat(http): add healthcheck endpoints liveness and readiness (#240)

* feat(http): add liveness and readiness endpoints

* feat(http): improve unhealthy msg

internal/http/health.go

@@ -0,0 +1,51 @@
+package http
+
+import (
+	"net/http"
+
+	"github.com/autobrr/autobrr/internal/database"
+
+	"github.com/go-chi/chi"
+)
+
+type healthHandler struct {
+	encoder encoder
+	db      *database.DB
+}
+
+func newHealthHandler(encoder encoder, db *database.DB) *healthHandler {
+	return &healthHandler{
+		encoder: encoder,
+		db:      db,
+	}
+}
+
+func (h healthHandler) Routes(r chi.Router) {
+	r.Get("/liveness", h.handleLiveness)
+	r.Get("/readiness", h.handleReadiness)
+}
+
+func (h healthHandler) handleLiveness(w http.ResponseWriter, _ *http.Request) {
+	writeHealthy(w)
+}
+
+func (h healthHandler) handleReadiness(w http.ResponseWriter, _ *http.Request) {
+	if err := h.db.Ping(); err != nil {
+		writeUnhealthy(w)
+		return
+	}
+
+	writeHealthy(w)
+}
+
+func writeHealthy(w http.ResponseWriter) {
+	w.Header().Set("Content-Type", "text/plain")
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte("OK"))
+}
+
+func writeUnhealthy(w http.ResponseWriter) {
+	w.Header().Set("Content-Type", "text/plain")
+	w.WriteHeader(http.StatusInternalServerError)
+	w.Write([]byte("Unhealthy. Database unreachable"))
+}