New Service Client: s3outposts

Reference: #15412
Reference: #15417

Also prepares the repository for `aws_s3control_*` resources, which will be included with the S3 on Outposts functionality.

Output from acceptance testing:

```
--- PASS: TestAccAWSProvider_Endpoints (5.73s)
```

.hashibot.hcl

@@ -490,6 +490,10 @@ behavior "regexp_issue_labeler_v2" "service_labels" {
     ],
     "service/s3control" = [
       "aws_s3_account_",
+      "aws_s3control_",
+    ],
+    "service/s3outposts" = [
+      "aws_s3outposts_",
     ],
     "service/sagemaker" = [
       "aws_sagemaker_",
@@ -1334,7 +1338,14 @@ behavior "pull_request_path_labeler" "service_labels" {
     "service/s3control" = [
       "aws/internal/service/s3control/**/*",
       "**/*_s3_account_*",
-      "**/s3_account_*"
+      "**/s3_account_*",
+      "**/*_s3control_*",
+      "**/s3control_*"
+    ]
+    "service/s3outposts" = [
+      "aws/internal/service/s3outposts/**/*",
+      "**/*_s3outposts_*",
+      "**/s3outposts_*"
     ]
     "service/sagemaker" = [
       "aws/internal/service/sagemaker/**/*",

aws/config.go

@@ -127,6 +127,7 @@ import (
 	"github.com/aws/aws-sdk-go/service/route53resolver"
 	"github.com/aws/aws-sdk-go/service/s3"
 	"github.com/aws/aws-sdk-go/service/s3control"
+	"github.com/aws/aws-sdk-go/service/s3outposts"
 	"github.com/aws/aws-sdk-go/service/sagemaker"
 	"github.com/aws/aws-sdk-go/service/secretsmanager"
 	"github.com/aws/aws-sdk-go/service/securityhub"
@@ -321,6 +322,7 @@ type AWSClient struct {
 	s3conn                              *s3.S3
 	s3connUriCleaningDisabled           *s3.S3
 	s3controlconn                       *s3control.S3Control
+	s3outpostsconn                      *s3outposts.S3Outposts
 	sagemakerconn                       *sagemaker.SageMaker
 	scconn                              *servicecatalog.ServiceCatalog
 	sdconn                              *servicediscovery.ServiceDiscovery
@@ -549,6 +551,7 @@ func (c *Config) Client() (interface{}, error) {
 		route53domainsconn:                  route53domains.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["route53domains"])})),
 		route53resolverconn:                 route53resolver.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["route53resolver"])})),
 		s3controlconn:                       s3control.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["s3control"])})),
+		s3outpostsconn:                      s3outposts.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["s3outposts"])})),
 		sagemakerconn:                       sagemaker.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["sagemaker"])})),
 		scconn:                              servicecatalog.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["servicecatalog"])})),
 		sdconn:                              servicediscovery.New(sess.Copy(&aws.Config{Endpoint: aws.String(c.Endpoints["servicediscovery"])})),

aws/provider.go

@@ -1176,6 +1176,7 @@ func init() {
 		"route53resolver",
 		"s3",
 		"s3control",
+		"s3outposts",
 		"sagemaker",
 		"sdb",
 		"secretsmanager",

infrastructure/repository/labels-service.tf

@@ -159,6 +159,7 @@ variable "service_labels" {
     "route53resolver",
     "s3",
     "s3control",
+    "s3outposts",
     "sagemaker",
     "savingsplans",
     "secretsmanager",

website/allowed-subcategories.txt

@@ -93,6 +93,8 @@ Route53 Domains
 Route53 Resolver
 Route53
 S3
+S3 Control
+S3 Outposts
 SES
 SNS
 SQS

website/docs/guides/custom-service-endpoints.html.md

@@ -170,6 +170,7 @@ The Terraform AWS Provider allows the following endpoints to be customized:
   <li><code>route53resolver</code></li>
   <li><code>s3</code></li>
   <li><code>s3control</code></li>
+  <li><code>s3outposts</code></li>
   <li><code>sagemaker</code></li>
   <li><code>sdb</code></li>
   <li><code>secretsmanager</code></li>