tests: improvements to acceptance testing (#128)

- update repo tests to create image repos
  in an organization, not a personal namespace.
  this is a more common use-case. and we're
  trying to discourage people in-product
  from creating personal namespaces

- add more docs on how to write new acceptance
  tests and run existing ones

Signed-off-by: Nick Santos <nick.santos@docker.com>

Author: nicks

CONTRIBUTING.md

@@ -57,17 +57,27 @@ Note, when you run the `terraform plan` you should see a warning, this ensures t
 
 Happy developing!
 
-## Testing
+## Acceptance Testing
 
-Run full test suite:
+WARNING: Acceptance tests run the provider with a real account against a real
+environment. They will create repositories, delete repositories, invite users to
+orgs, etc.
 
-```shell
-make testacc
+Only run them with account credentials that are ok for testing!
+
+### Adding a new test
+
+If you're contributing a new test, set up your credentials:
+
+```
+export DOCKER_USERNAME=[your-username]
+export DOCKER_PASSWORD=[your-password]
+export ACCTEST_DOCKER_ORG=[an-org-you-belong-to]
 ```
 
-Run a specific test(s):
+Then run:
 
-```shell
+```
 make testacc TESTS=TestAccXXX
 ```
 
@@ -79,6 +89,36 @@ TF_ACC=1 go test ./... -v -count 1 -parallel 20 -timeout 120m -run TestAccXXX
 
 where `TestAccXXX` is the testing function within the `_test.go` file.
 
+New tests should create resources under the org namespace
+`envvar.AccTestOrganization`. See existing tests for examples.
+
+### Running the full test suite
+
+Only Docker employees can currently run the full acceptance suite,
+because they use the stage environment.
+
+To run the tests on Github Actions on main, run:
+
+```
+gh workflow run acctest.yaml
+```
+
+To run it on a specific branch, run:
+
+```
+gh workflow run acctest.yaml -f ref=[git-sha|branch-name]
+```
+
+To run it locally, you will need credentials for our test account. 
+The password is in the terraform-provider-docker 1password vault.
+
+```
+export DOCKER_HUB_HOST=hub-stage.docker.com
+export DOCKER_USERNAME=dockerterraformacctest
+export DOCKER_PASSWORD=[password]
+make testacc
+```
+
 ## Environment Variables
 
 ```shell

internal/provider/resource_repository_test.go

@@ -18,15 +18,15 @@ package provider
 
 import (
 	"fmt"
-	"os"
 	"testing"
 
+	"github.com/docker/terraform-provider-docker/internal/envvar"
 	"github.com/hashicorp/terraform-plugin-testing/helper/resource"
 	"github.com/hashicorp/terraform-plugin-testing/terraform"
 )
 
 func TestAccRepositoryResource(t *testing.T) {
-	namespace := os.Getenv("DOCKER_USERNAME")
+	namespace := envvar.GetWithDefault(envvar.AccTestOrganization)
 	name := "example-repo" + randString(10)
 	resource.Test(t, resource.TestCase{
 		PreCheck:                 func() { testAccPreCheck(t) },
@@ -65,7 +65,7 @@ func TestAccRepositoryResource(t *testing.T) {
 }
 
 func TestAccRepositoryResource_Upgrade(t *testing.T) {
-	namespace := os.Getenv("DOCKER_USERNAME")
+	namespace := envvar.GetWithDefault(envvar.AccTestOrganization)
 	name := "example-repo" + randString(10)
 	resource.Test(t, resource.TestCase{
 		PreCheck: func() { testAccPreCheck(t) },
@@ -117,7 +117,7 @@ resource "docker_hub_repository" "test" {
 }
 
 func TestAccRepositoryResourceImmutableTags(t *testing.T) {
-	namespace := os.Getenv("DOCKER_USERNAME")
+	namespace := envvar.GetWithDefault(envvar.AccTestOrganization)
 	name := "immutable-repo" + randString(10)
 	resource.Test(t, resource.TestCase{
 		PreCheck:                 func() { testAccPreCheck(t) },