Add validation for start_time to resource_policy

Signed-off-by: Modular Magician <magic-modules@google.com>

google/resource_compute_resource_policy.go

@@ -92,9 +92,10 @@ which cannot be a dash.`,
 													Description: `The number of days between snapshots.`,
 												},
 												"start_time": {
-													Type:     schema.TypeString,
-													Required: true,
-													ForceNew: true,
+													Type:         schema.TypeString,
+													Required:     true,
+													ForceNew:     true,
+													ValidateFunc: validateHourlyOnly,
 													Description: `This must be in UTC format that resolves to one of
 00:00, 04:00, 08:00, 12:00, 16:00, or 20:00. For example,
 both 13:00-5 and 08:00 are valid.`,
@@ -118,9 +119,10 @@ both 13:00-5 and 08:00 are valid.`,
 													Description: `The number of hours between snapshots.`,
 												},
 												"start_time": {
-													Type:     schema.TypeString,
-													Required: true,
-													ForceNew: true,
+													Type:         schema.TypeString,
+													Required:     true,
+													ForceNew:     true,
+													ValidateFunc: validateHourlyOnly,
 													Description: `Time within the window to start the operations.
 It must be in format "HH:MM",
 where HH : [00-23] and MM : [00-00] GMT.`,

google/validation.go

@@ -261,3 +261,16 @@ func StringNotInSlice(invalid []string, ignoreCase bool) schema.SchemaValidateFu
 		return
 	}
 }
+
+// Ensure that hourly timestamp strings "HH:MM" have the minutes zeroed out for hourly only inputs
+func validateHourlyOnly(val interface{}, key string) (warns []string, errs []error) {
+	v := val.(string)
+	parts := strings.Split(v, ":")
+	if len(parts) != 2 {
+		errs = append(errs, fmt.Errorf("%q must be in the format HH:00, got: %s", key, v))
+	}
+	if parts[1] != "00" {
+		errs = append(errs, fmt.Errorf("%q does not allow minutes, it must be in the format HH:00, got: %s", key, v))
+	}
+	return
+}