Add credstash implementation to obtain db password

[rncain]

I added a credstash implementation if wanted. Instead of requiring the user to add passwords to the config, the loader will use credstash in realtime to obtain the db password.

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[IanMeyers]

Thanks for this. I don't see that there's region support when setting up the credstash - is that something that you could add? Important this this solution be region locked based on the deployed location.