Allow periods in parameter group names for RDS

[autotune]

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Terraform Version

Terraform v0.12.21 (same with 0.12.20)

* provider.aws v2.50.0

Affected Resource(s)

* aws_db_parameter_group

Terraform Configuration Files

resource "aws_db_parameter_group" "default-postgres9-6" {
    name        = "default.postgres9.6"
    family      = "postgres9.6"
    description = "Default parameter group for postgres9.6"
... rest is not relevant ...
}

Debug Output

Partial output https://gist.github.com/iMartyn/09aea39aff770335ce533ca3373a27c0#file-terraform-debug-txt - too much useful information to others in the full output to make that public.

Panic Output

No panic, just errors

Expected Behavior

Given that this resource exists on aws, I should be able to import it into terraform.

Actual Behavior

Cannot execute plan

Error: only lowercase alphanumeric characters and hyphens allowed in parameter group "name"

  on dbpg.tf line 1874, in resource "aws_db_parameter_group" "default-postgres9-6":
1874: resource "aws_db_parameter_group" "default-postgres9-6" {

Steps to Reproduce

1. create pg database point and click and then use something like terraforming to create terraform to import resources into.  or just create a db parameter group name with something like the hcl above.

2. `terraform plan`

Important Factoids

The DB was pre-existing, I'm trying to import everything into terraform that has been created by point-and-click.

References

I'm not the only one facing this problem : https://stackoverflow.com/questions/57386371/terraform-rds-instance-errors-with-lowercase-alphanumeric-characters-and-hypens

Relations

Closes #12144

Output from Acceptance Testing

terraform-provider-aws % make testacc TESTS=TestValidParamGroupName PKG=rds
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/rds/... -v -count 1 -parallel 20 -run='TestValidParamGroupName'  -timeout 360m
=== RUN   TestValidParamGroupName
=== PAUSE TestValidParamGroupName
=== CONT  TestValidParamGroupName
--- PASS: TestValidParamGroupName (0.00s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/rds	3.720s

terraform import aws_db_parameter_group.default-mysql default.aurora-mysql8.0

Import successful!

The resources that were imported are shown above. These resources are now in
your Terraform state and will henceforth be managed by Terraform.

[github-actions]

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[jar-b]

LGTM 🎉

% make testacc PKG=rds TESTS=TestAccRDSParameterGroup_
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/rds/... -v -count 1 -parallel 20 -run='TestAccRDSParameterGroup_'  -timeout 360m

--- PASS: TestAccRDSParameterGroup_disappears (26.68s)
--- PASS: TestAccRDSParameterGroup_namePrefix (31.83s)
--- PASS: TestAccRDSParameterGroup_only (32.67s)
--- PASS: TestAccRDSParameterGroup_matchDefault (32.87s)
--- PASS: TestAccRDSParameterGroup_generatedName (37.97s)
--- PASS: TestAccRDSParameterGroup_withApplyMethod (39.45s)
--- PASS: TestAccRDSParameterGroup_updateParameters (60.20s)
--- PASS: TestAccRDSParameterGroup_caseParameters (63.82s)
--- PASS: TestAccRDSParameterGroup_basic (82.67s)
--- PASS: TestAccRDSParameterGroup_limit (83.37s)
--- PASS: TestAccRDSParameterGroup_caseWithMixedParameters (84.01s)
--- PASS: TestAccRDSParameterGroup_tags (86.84s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/rds        89.978s

% make testacc PKG=rds TESTS=TestAccRDSClusterParameterGroup_
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/rds/... -v -count 1 -parallel 20 -run='TestAccRDSClusterParameterGroup_'  -timeout 360m

--- PASS: TestAccRDSClusterParameterGroup_disappears (28.79s)
--- PASS: TestAccRDSClusterParameterGroup_dynamicDiffs (33.26s)
--- PASS: TestAccRDSClusterParameterGroup_generatedName (34.97s)
--- PASS: TestAccRDSClusterParameterGroup_only (36.13s)
--- PASS: TestAccRDSClusterParameterGroup_GeneratedName_parameter (36.58s)
--- PASS: TestAccRDSClusterParameterGroup_withApplyMethod (37.44s)
--- PASS: TestAccRDSClusterParameterGroup_NamePrefix_parameter (37.46s)
--- PASS: TestAccRDSClusterParameterGroup_namePrefix (37.65s)
--- PASS: TestAccRDSClusterParameterGroup_caseParameters (49.68s)
--- PASS: TestAccRDSClusterParameterGroup_updateParameters (51.79s)
--- PASS: TestAccRDSClusterParameterGroup_tags (64.55s)
--- PASS: TestAccRDSClusterParameterGroup_basic (70.78s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/rds        73.938s

[jar-b]

Note that custom group names still cannot be created using periods, however, this should prevent the provider side validation failures when default parameter groups are imported and used as inputs to other resources. These default groups cannot be updated once imported (AWS does not allow modification of default parameter groups).

[jar-b]

Thanks for your contribution, @autotune! 👏

[github-actions]

This functionality has been released in v5.21.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.