fix(rdsinstance/dbinstance): check optiongroupname correctly

[wotolom]

Description of your changes

In the controllers of the resources database RDSInstance and rds DBInstance an extra check for the parameter OptionGroupName is added as this needs to be checked against the entries of OptionGroupMemberships given by the Describe output.

Fixes #1795 (similar CloudwatchLogsExportConfiguration issue will be addressed in separate PR)

Note: rds DBCluster also has the field OptionGroupName , so I tried implementing the same logic here too. However I got this error:

create failed: cannot create DBCluster in AWS: InvalidParameterCombination: Option groups are not supported for DB Clusters

So one may consider removing the field here? (see also no such field
at terraform: https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/rds_cluster)

I have:

• Read and followed Crossplane's [contribution process].
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Manually

[MisterMX]

It appears that it is not possible to associate a custom option group with a DB cluster. From the AWS Docs:

--option-group-name (string)
The option group to associate the DB cluster with.
DB clusters are associated with a default option group that can’t be modified.

I guess they copied this field from the DB instance API to be implemented in the future? Terraform probably skipped it because it is not supported until now.

Since the provider is meant to be a 1:1 reflection of the AWS API I would keep this field despite its lack of use.

[MisterMX]

LGTM. Thank you very much for your contribution @wotolom!