expand_string? interface method so plugins can decide whether or not to expand the string

[tongueroo]

This is a 🐞 bug fix.
This is a 🙋‍♂️ feature or enhancement.

• I've added tests (if it's a bug, feature or enhancement)
• I've adjusted the documentation (if it's a feature or enhancement)
• The test suite passes (run bundle exec rspec to verify this)

Summary

Add an expand_string? interface method for plugin expanders.

Context

• https://community.boltops.com/t/terraspace-aws-backend-undefined-method/790
• implement expand_string? to not expand aws arn values terraspace_plugin_aws#10

How to Test

Try a ruby DSL backend.rb like so:

backend.rb

backend("s3",
  bucket:                      'terraform-state-demo-:ACCOUNT-:REGION-:ENV',
  key:                         ':REGION/:ENV/:BUILD_DIR/terraform.tfstate',
  region:                      ":REGION",
  encrypt:                     true,
  dynamodb_table:              "terraform_locks",
  acl:                         "private",
  kms_key_id:                  "arn:aws:kms:us-west-2:112233445566:key/937e938d-02f7-458c-8f9b-30846afd3bd3",
)

Version Changes

Patch

[tongueroo]

Released in v0.6.20