fix: cron validation support for star step value (#1302)

## Fixes Or Enhances
Resolves #1259

**Make sure that you've checked the boxes below before you submit PR:**
- [x] Tests exist or have been written that cover this particular
change.

@go-playground/validator-maintainers

Author: cgetzen

regexes.go

@@ -73,7 +73,7 @@ const (
 	cveRegexString                   = `^CVE-(1999|2\d{3})-(0[^0]\d{2}|0\d[^0]\d{1}|0\d{2}[^0]|[1-9]{1}\d{3,})$` // CVE Format Id https://cve.mitre.org/cve/identifiers/syntaxchange.html
 	mongodbIdRegexString             = "^[a-f\\d]{24}$"
 	mongodbConnStringRegexString     = "^mongodb(\\+srv)?:\\/\\/(([a-zA-Z\\d]+):([a-zA-Z\\d$:\\/?#\\[\\]@]+)@)?(([a-z\\d.-]+)(:[\\d]+)?)((,(([a-z\\d.-]+)(:(\\d+))?))*)?(\\/[a-zA-Z-_]{1,64})?(\\?(([a-zA-Z]+)=([a-zA-Z\\d]+))(&(([a-zA-Z\\d]+)=([a-zA-Z\\d]+))?)*)?$"
-	cronRegexString                  = `(@(annually|yearly|monthly|weekly|daily|hourly|reboot))|(@every (\d+(ns|us|µs|ms|s|m|h))+)|((((\d+,)+\d+|(\d+(\/|-)\d+)|\d+|\*) ?){5,7})`
+	cronRegexString                  = `(@(annually|yearly|monthly|weekly|daily|hourly|reboot))|(@every (\d+(ns|us|µs|ms|s|m|h))+)|((((\d+,)+\d+|((\*|\d+)(\/|-)\d+)|\d+|\*) ?){5,7})`
 	spicedbIDRegexString             = `^(([a-zA-Z0-9/_|\-=+]{1,})|\*)$`
 	spicedbPermissionRegexString     = "^([a-z][a-z0-9_]{1,62}[a-z0-9])?$"
 	spicedbTypeRegexString           = "^([a-z][a-z0-9_]{1,61}[a-z0-9]/)?[a-z][a-z0-9_]{1,62}[a-z0-9]$"

validator_test.go

@@ -13656,6 +13656,7 @@ func TestCronExpressionValidation(t *testing.T) {
 		{"*/20 * * * *", "cron", true},
 		{"0 15 10 ? * MON-FRI", "cron", true},
 		{"0 15 10 ? * 6#3", "cron", true},
+		{"0 */15 * * *", "cron", true},
 		{"wrong", "cron", false},
 	}