resource/aws_db_option_group: Read option attribute into Terraform state and skip ModifyOptionGroup when no option updates

[bflad]

Closes #209 (covered by TestAccAWSDBOptionGroup_Option_OptionSettings_IAMRole)
Fixes #1167 (covered by ImportState TestStep added to all acceptance tests)
Closes #1876 (covered by TestAccAWSDBOptionGroup_Option_OptionSettings_MultipleNonDefault)
Fixes #6365 (covered by ImportState TestStep added to all acceptance tests)
Fixes #7114 (covered by TestAccAWSDBOptionGroup_Tags_WithOptions)

Previously, this Terraform resource was not able to perform any drift detection on or import the state of the option attribute. The caveat is that while RDS returns only modified options, it will return all option settings whether modified or not from their default values. To workaround this option settings issue, we pass in the options from the Terraform configuration and ignore default values that are not present in the configuration.

This also fixes an issue on update where ModifyOptionGroup was being called without any actual option updates, which would generate an error and prevent other updates from occurring. While the update logic was correctly using d.HasChange() before, when working with complex TypeSet attributes like option it can apparently be fooled. We use similar length check logic in the aws_db_parameter_group resource for example.

Output from acceptance testing (AWS Standard):

--- PASS: TestAccAWSDBOptionGroup_timeoutBlock (13.50s)
--- PASS: TestAccAWSDBOptionGroup_generatedName (13.50s)
--- PASS: TestAccAWSDBOptionGroup_namePrefix (13.58s)
--- PASS: TestAccAWSDBOptionGroup_basic (13.67s)
--- PASS: TestAccAWSDBOptionGroup_multipleOptions (14.08s)
--- PASS: TestAccAWSDBOptionGroup_sqlServerOptionsUpdate (23.90s)
--- PASS: TestAccAWSDBOptionGroup_Option_OptionSettings (27.86s)
--- PASS: TestAccAWSDBOptionGroup_Option_OptionSettings_MultipleNonDefault (29.37s)
--- PASS: TestAccAWSDBOptionGroup_OracleOptionsUpdate (32.14s)
--- PASS: TestAccAWSDBOptionGroup_Option_OptionSettings_IAMRole (32.40s)
--- PASS: TestAccAWSDBOptionGroup_Tags (38.88s)
--- PASS: TestAccAWSDBOptionGroup_Tags_WithOptions (43.07s)
--- PASS: TestAccAWSDBOptionGroup_basicDestroyWithInstance (499.04s)

Output from acceptance testing (AWS GovCloud (US), failures will be separately addressed with other GovCloud fixes):

--- FAIL: TestAccAWSDBOptionGroup_OracleOptionsUpdate (12.33s)
    testing.go:538: Step 0 error: Error applying: 1 error occurred:
        	* aws_db_option_group.bar: 1 error occurred:
        	* aws_db_option_group.bar: Error modifying DB Option Group: InvalidParameterValue: Version 12.1.0.4.v1 is invalid for OEM_AGENT option. Valid versions are 13.2.0.0.v1,13.2.0.0.v2
        	status code: 400, request id: 748c6b88-9406-436b-b755-461feb20abbf

--- PASS: TestAccAWSDBOptionGroup_namePrefix (14.68s)
--- PASS: TestAccAWSDBOptionGroup_basic (14.73s)
--- PASS: TestAccAWSDBOptionGroup_generatedName (14.80s)
--- PASS: TestAccAWSDBOptionGroup_timeoutBlock (14.82s)
--- PASS: TestAccAWSDBOptionGroup_multipleOptions (15.53s)
--- FAIL: TestAccAWSDBOptionGroup_Option_OptionSettings_IAMRole (19.14s)
    testing.go:538: Step 0 error: Check failed: Check 4/4 error: Expected option setting to be a valid IAM role but received arn:aws-us-gov:iam::--OMITTED--:role/rds-backup-option-group-test-terraform-0w89k
--- PASS: TestAccAWSDBOptionGroup_sqlServerOptionsUpdate (25.33s)
--- PASS: TestAccAWSDBOptionGroup_Option_OptionSettings_MultipleNonDefault (26.42s)
--- PASS: TestAccAWSDBOptionGroup_Option_OptionSettings (28.46s)
--- PASS: TestAccAWSDBOptionGroup_Tags (35.49s)
--- PASS: TestAccAWSDBOptionGroup_Tags_WithOptions (39.27s)
--- PASS: TestAccAWSDBOptionGroup_basicDestroyWithInstance (498.37s)

[mbfrahry]

LGTM

[bflad]

This has been released in version 1.56.0 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!