Alerting Rule Group: Suppress duration equivalent diffs (#941)

Closes #861
When setting 60m, the API returns 1h. Also added a duration validation

Author: julienduchesne

examples/resources/grafana_rule_group/_acc_multi_rule_group.tf

@@ -9,7 +9,7 @@ resource "grafana_rule_group" "my_multi_alert_group" {
   org_id           = 1
   rule {
     name           = "My Alert Rule 1"
-    for            = "2m"
+    for            = "60m"
     condition      = "B"
     no_data_state  = "NoData"
     exec_err_state = "Alerting"

examples/resources/grafana_rule_group/_acc_multi_rule_group_added.tf

@@ -9,7 +9,7 @@ resource "grafana_rule_group" "my_multi_alert_group" {
   org_id           = 1
   rule {
     name           = "My Alert Rule 1"
-    for            = "2m"
+    for            = "1h"
     condition      = "B"
     no_data_state  = "NoData"
     exec_err_state = "Alerting"

examples/resources/grafana_rule_group/_acc_multi_rule_group_subtracted.tf

@@ -9,7 +9,7 @@ resource "grafana_rule_group" "my_multi_alert_group" {
   org_id           = 1
   rule {
     name           = "My Alert Rule 1"
-    for            = "2m"
+    for            = "1h"
     condition      = "B"
     no_data_state  = "NoData"
     exec_err_state = "Alerting"

internal/common/schema.go

@@ -4,7 +4,10 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+	"time"
 
+	"github.com/hashicorp/go-cty/cty"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 )
 
@@ -50,3 +53,12 @@ func CloneResourceSchemaForDatasource(r *schema.Resource, updates map[string]*sc
 func AllowedValuesDescription(description string, allowedValues []string) string {
 	return fmt.Sprintf("%s. Allowed values: `%s`.", description, strings.Join(allowedValues, "`, `"))
 }
+
+func ValidateDuration(i interface{}, p cty.Path) diag.Diagnostics {
+	v := i.(string)
+	_, err := time.ParseDuration(v)
+	if err != nil {
+		return diag.Errorf("%q is not a valid duration: %s", v, err)
+	}
+	return nil
+}

internal/resources/cloud/resource_cloud_stack.go

@@ -14,7 +14,6 @@ import (
 
 	gapi "github.com/grafana/grafana-api-golang-client"
 	"github.com/grafana/terraform-provider-grafana/internal/common"
-	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/retry"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
@@ -86,17 +85,10 @@ available at “https://<stack_slug>.grafana.net".`,
 				DiffSuppressFunc: func(_, _, newValue string, _ *schema.ResourceData) bool { return newValue == "false" },
 			},
 			"wait_for_readiness_timeout": {
-				Type:     schema.TypeString,
-				Optional: true,
-				Default:  defaultReadinessTimeout.String(),
-				ValidateDiagFunc: func(i interface{}, p cty.Path) diag.Diagnostics {
-					v := i.(string)
-					_, err := time.ParseDuration(v)
-					if err != nil {
-						return diag.Errorf("%q is not a valid duration: %s", v, err)
-					}
-					return nil
-				},
+				Type:             schema.TypeString,
+				Optional:         true,
+				Default:          defaultReadinessTimeout.String(),
+				ValidateDiagFunc: common.ValidateDuration,
 				// Only used when wait_for_readiness is true
 				DiffSuppressFunc: func(_, _, newValue string, d *schema.ResourceData) bool {
 					return newValue == defaultReadinessTimeout.String()

internal/resources/grafana/resource_alerting_rule_group.go

@@ -76,10 +76,16 @@ This resource requires Grafana 9.1.0 or later.
 							Description: "The name of the alert rule.",
 						},
 						"for": {
-							Type:        schema.TypeString,
-							Optional:    true,
-							Default:     0,
-							Description: "The amount of time for which the rule must be breached for the rule to be considered to be Firing. Before this time has elapsed, the rule is only considered to be Pending.",
+							Type:             schema.TypeString,
+							Optional:         true,
+							Default:          0,
+							Description:      "The amount of time for which the rule must be breached for the rule to be considered to be Firing. Before this time has elapsed, the rule is only considered to be Pending.",
+							ValidateDiagFunc: common.ValidateDuration,
+							DiffSuppressFunc: func(k, oldValue, newValue string, d *schema.ResourceData) bool {
+								oldDuration, _ := time.ParseDuration(oldValue)
+								newDuration, _ := time.ParseDuration(newValue)
+								return oldDuration == newDuration
+							},
 						},
 						"no_data_state": {
 							Type:        schema.TypeString,