@GetMapping("/{id}")
    public ShenyuAdminResult detailRule(@Valid @PathVariable("id")
                                        @Existed(provider = RuleMapper.class, message = "rule is not existed") final String id) {
        RuleVO ruleVO = ruleService.findById(id);
        return ShenyuAdminResult.success(ShenyuResultMessage.DETAIL_SUCCESS, ruleVO);
    }
detail rule.

@param id rule id.
@return {@linkplain ShenyuAdminResult}
shenyu-admin/src/main/java/org/apache/shenyu/admin/controller/RuleController.java