Allow use of Systems Manager Parameters instead of Secrets Manager Secrets

[KyleKotowick]

Is your feature request related to a problem? Please describe.
This application currently only supports Secrets Manager for remote secret storage. Secrets Manager is $0.40/secret/month.

Systems Manager Parameters are equally secure (can be KMS encrypted) and are free. Since none of the other Secrets Manager features are necessary for this application (rotation, replication), use of Secrets Manager is not strictly required.

Therefore, Systems Manager Parameters would be a preferred secret store for some users.

Describe the solution you'd like
Allow specifying Systems Manager parameter names/ARNs instead of only allowing hard-coded Secret names.

Describe alternatives you've considered
Keep using secrets.

[bartelemi]

I second this a lot. This tool currently requires provisioning 6 secrets, where in reality it could be reduced to 1 or even 0 if it supported parameter store.

IMHO it should be up to users to decide how they want to store the secrets.

In my case, I use this tool maybe once every few months but I have to pay for it $2.4 each month just for the secrets. I could take my team for ice cream every quarter for that money! 😄

[ChrisPates]

I'm currently working on some refactoring to address a number of other issues.

However, I do concur that we should support parameters store as an alternative to secrets manager.

Definitely the first time I've had frugality represented in terms of ice cream!

[morganrowse]

Heya, a simpler fix here may just be to save all of the secrets into a single secret rather than 6 individual ones. Ill see if I can get a PR together.

Edit: I was not able to get this together

[ChrisPates]

This request has been merged with related one under a single feature request [Expand the Options for storing the sensitive parameters to include binaray secrets and SSM Parameter Store #180](https://github.com/awslabs/ssosync/issues/180]. Please review and add any specific requirements you feel it doesn't address.