Correctly capturing return codes from executed programs

Return codes were not being correctly captured for executed programs. Thus an executed program would always return 0 to the shell / executing program.

By passing on the return codes, the calling program can correctly capture and raise errors.

Override using env vars and using Get-Parameters-By-Path

In this release, there is

• support for keeping existing environment variables via the -priority_env_vars switch. By default any AWS SSM Parameters with the same name will override existing environment variables.
• Change from Describe to get-parameters-by-path (more efficient use of the AWS API to prevent "Rate execeeded" errors. https://repost.aws/knowledge-center/ssm-parameter-store-rate-exceeded .

This release additional displays a warning when :

• Parameters cannot be discovered for a given parameter store path
• Environment variables will be overwritten or ignored as the variable exists in the environment

Move from Popen to Run for subprocess

Popen starts a sub-process and returns control back to the console completing the task early. By using run instead the process can be run to completion, allowing time for the executing command to be completed as it is a synchronous operation.

Initial Release

This is the initial release of chamber. Chamber can be used to hydrate environment secrets from the SSM Parameter store into environment variables which can be utilised by a calling program.