* Allow having empty paths in *path operations* used with `include_router` and a `prefix`.
    * This allows having a router for `/cats` and all its *path operations*, while having one of them for `/cats`.
    * Now it doesn't have to be only `/cats/` (with a trailing slash).
    * To use it, declare the path in the *path operation* as the empty string (`""`).

border-top: var(--#{$prefix}card-border-width) solid var(--#{$prefix}card-border-color);\n\n  &:last-child {\n    @include border-radius(0 0 var(--#{$prefix}card-inner-border-radius) var(--#{$prefix}card-inner-border-radius));\n  }\n}\n\n\n//\n// Header navs\n//\n\n.card-header-tabs {\n  margin-right: calc(-.5 * var(--#{$prefix}card-cap-padding-x)); // stylelint-disable-line function-disallowed-list\n  margin-bottom: calc(-1 * var(--#{$prefix}card-cap-padding-y)); // stylelint-disable-line function-disallowed-list\n...

color: $card-cap-color;\n  background-color: $card-cap-bg;\n  border-top: $card-border-width solid $card-border-color;\n\n  &:last-child {\n    @include border-radius(0 0 $card-inner-border-radius $card-inner-border-radius);\n  }\n}\n\n\n//\n// Header navs\n//\n\n.card-header-tabs {\n  margin-right: -$card-spacer-x * .5;\n  margin-bottom: -$card-spacer-y;\n  margin-left: -$card-spacer-x * .5;\n  border-bottom: 0;\n}\n\n.card-header-pills {\n  margin-right: -$card-spacer-x * .5;\n  margin-left: -$card-spacer-x...