provider/aws: Support `snapshot_name` for ElastiCache Cluster and (#8419)

Replication Groups

In order to be able to restore a named snapshot as ElastiCache Cluster
or a Replication Group, the `snapshot_name` parameter was needed to be
passed. Changing the `snapshot_name` will force a new resource to be
created

```

```

builtin/providers/aws/resource_aws_elasticache_cluster.go

@@ -81,6 +81,11 @@ func resourceAwsElastiCacheCommonSchema() map[string]*schema.Schema {
 			Optional: true,
 			Computed: true,
 		},
+		"snapshot_name": &schema.Schema{
+			Type:     schema.TypeString,
+			Optional: true,
+			ForceNew: true,
+		},
 
 		"maintenance_window": &schema.Schema{
 			Type:     schema.TypeString,
@@ -220,8 +225,8 @@ func resourceAwsElasticacheClusterCreate(d *schema.ResourceData, meta interface{
 
 	securityNames := expandStringList(securityNameSet.List())
 	securityIds := expandStringList(securityIdSet.List())
-
 	tags := tagsFromMapEC(d.Get("tags").(map[string]interface{}))
+
 	req := &elasticache.CreateCacheClusterInput{
 		CacheClusterId:          aws.String(clusterId),
 		CacheNodeType:           aws.String(nodeType),
@@ -263,6 +268,10 @@ func resourceAwsElasticacheClusterCreate(d *schema.ResourceData, meta interface{
 		log.Printf("[DEBUG] Restoring Redis cluster from S3 snapshot: %#v", s)
 	}
 
+	if v, ok := d.GetOk("snapshot_name"); ok {
+		req.SnapshotName = aws.String(v.(string))
+	}
+
 	if v, ok := d.GetOk("az_mode"); ok {
 		req.AZMode = aws.String(v.(string))
 	}
@@ -292,7 +301,7 @@ func resourceAwsElasticacheClusterCreate(d *schema.ResourceData, meta interface{
 	// name contained uppercase characters.
 	d.SetId(strings.ToLower(*resp.CacheCluster.CacheClusterId))
 
-	pending := []string{"creating"}
+	pending := []string{"creating", "modifying", "restoring"}
 	stateConf := &resource.StateChangeConf{
 		Pending:    pending,
 		Target:     []string{"available"},

builtin/providers/aws/resource_aws_elasticache_replication_group.go

@@ -126,6 +126,10 @@ func resourceAwsElasticacheReplicationGroupCreate(d *schema.ResourceData, meta i
 		params.SnapshotWindow = aws.String(v.(string))
 	}
 
+	if v, ok := d.GetOk("snapshot_name"); ok {
+		params.SnapshotName = aws.String(v.(string))
+	}
+
 	resp, err := conn.CreateReplicationGroup(params)
 	if err != nil {
 		return fmt.Errorf("Error creating Elasticache Replication Group: %s", err)
@@ -133,7 +137,7 @@ func resourceAwsElasticacheReplicationGroupCreate(d *schema.ResourceData, meta i
 
 	d.SetId(*resp.ReplicationGroup.ReplicationGroupId)
 
-	pending := []string{"creating", "modifying"}
+	pending := []string{"creating", "modifying", "restoring"}
 	stateConf := &resource.StateChangeConf{
 		Pending:    pending,
 		Target:     []string{"available"},

website/source/docs/providers/aws/r/elasticache_cluster.html.markdown

@@ -85,6 +85,8 @@ names to associate with this cache cluster
 Amazon Resource Name (ARN) of a Redis RDB snapshot file stored in Amazon S3.
 Example: `arn:aws:s3:::my_bucket/snapshot1.rdb`
 
+* `snapshot_name` - (Optional) The name of a snapshot from which to restore data into the new node group.  Changing the `snapshot_name` forces a new resource. 
+
 * `snapshot_window` - (Optional, Redis only) The daily time range (in UTC) during which ElastiCache will
 begin taking a daily snapshot of your cache cluster. Example: 05:00-09:00
 

website/source/docs/providers/aws/r/elasticache_replication_group.html.markdown

@@ -31,7 +31,7 @@ resource "aws_elasticache_replication_group" "bar" {
 
 The following arguments are supported:
 
-* `replication_group_id` – (Required) The replication group identifier.
+* `replication_group_id` – (Required) The replication group identifier. This parameter is stored as a lowercase string.
 * `replication_group_description` – (Required) A user-created description for the replication group.
 * `number_cache_clusters` - (Required) The number of cache clusters this replication group will have.
  If Multi-AZ is enabled , the value of this parameter must be at least 2. Changing this number will force a new resource
@@ -46,6 +46,7 @@ The following arguments are supported:
 * `snapshot_arns` – (Optional) A single-element string list containing an
 Amazon Resource Name (ARN) of a Redis RDB snapshot file stored in Amazon S3.
 Example: `arn:aws:s3:::my_bucket/snapshot1.rdb`
+* `snapshot_name` - (Optional) The name of a snapshot from which to restore data into the new node group. Changing the `snapshot_name` forces a new resource. 
 * `maintenance_window` – (Optional) Specifies the weekly time range for when maintenance
 on the cache cluster is performed. The format is `ddd:hh24:mi-ddd:hh24:mi` (24H Clock UTC).
 The minimum maintenance window is a 60 minute period. Example: `sun:05:00-sun:09:00`
@@ -66,5 +67,4 @@ Please note that setting a `snapshot_retention_limit` is not supported on cache.
 
 The following attributes are exported:
 
-* `id` - The ID of the ElastiCache Replication Group
-* `primary_endpoint_address` - The Address of the Primary Node in the replication group. Doesn't include the port.
+* `id` - The ID of the ElastiCache Replication Group