feat(health): add health checking endpoints and logic

Introduce health checking functionality with liveness and readiness 
endpoints to monitor the application's status. Implement a health 
checker that verifies database connectivity and provides a simple 
liveness check. Update service routing to use the new health 
checker functionality. Add corresponding unit tests for validation.

health/health_test.go

@@ -0,0 +1,75 @@
+package health
+
+import (
+	"database/sql"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLivenessHandler(t *testing.T) {
+	logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
+	db, _, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	checker := New(db, logger)
+
+	req := httptest.NewRequest(http.MethodGet, "/health/live", nil)
+	rec := httptest.NewRecorder()
+
+	checker.LivenessHandler(rec, req)
+
+	assert.Equal(t, http.StatusOK, rec.Code)
+	assert.Contains(t, rec.Body.String(), `"status":"UP"`)
+}
+
+func TestReadinessHandler_Healthy(t *testing.T) {
+	logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
+	db, mock, err := sqlmock.New(sqlmock.MonitorPingsOption(true))
+	require.NoError(t, err)
+	defer db.Close()
+
+	// Expect a ping and return success
+	mock.ExpectPing().WillReturnError(nil)
+
+	checker := New(db, logger)
+
+	req := httptest.NewRequest(http.MethodGet, "/health/ready", nil)
+	rec := httptest.NewRecorder()
+
+	checker.ReadinessHandler(rec, req)
+
+	assert.Equal(t, http.StatusOK, rec.Code)
+	assert.Contains(t, rec.Body.String(), `"status":"UP"`)
+	assert.Contains(t, rec.Body.String(), `"database":"UP"`)
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestReadinessHandler_DatabaseDown(t *testing.T) {
+	logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
+	db, mock, err := sqlmock.New(sqlmock.MonitorPingsOption(true))
+	require.NoError(t, err)
+	defer db.Close()
+
+	// Expect a ping and return error
+	mock.ExpectPing().WillReturnError(sql.ErrConnDone)
+
+	checker := New(db, logger)
+
+	req := httptest.NewRequest(http.MethodGet, "/health/ready", nil)
+	rec := httptest.NewRecorder()
+
+	checker.ReadinessHandler(rec, req)
+
+	assert.Equal(t, http.StatusServiceUnavailable, rec.Code)
+	assert.Contains(t, rec.Body.String(), `"status":"DOWN"`)
+	assert.Contains(t, rec.Body.String(), `"database":"DOWN"`)
+	assert.NoError(t, mock.ExpectationsWereMet())
+}