secret helper methods expansion support

[tongueroo]

Related:

• https://github.com/boltops-tools/terraspace_plugin_azurerm/pull/10
• https://github.com/boltops-tools/terraspace_plugin_aws/pull/17
• https://github.com/boltops-tools/terraspace_plugin_google/pull/9
• https://github.com/boltops-tools/terraspace/pull/185

Docs:

• https://terraspace.cloud/docs/helpers/aws/secrets/
• https://terraspace.cloud/docs/helpers/aws/ssm/
• https://terraspace.cloud/docs/helpers/azure/secrets/
• https://terraspace.cloud/docs/helpers/google/secrets/