bootstrap/scss/mixins/_container.scss

// Container mixins

@mixin make-container($gutter: $container-padding-x) {
  --bs-gutter-x: #{$gutter};

  width: 100%;
  padding-right: var(--bs-gutter-x);
  padding-left: var(--bs-gutter-x);
  margin-right: auto;
  margin-left: auto;
}