auth variable should be passed as a map instead of list

[cdobbyn]

Describe the Bug

If you have multiple auths attached to your proxy the index can change over time, this means auths are added/removed dangerously from the resource.

Expected Behavior

The "dynamic" auth on the proxy resource continues to function with a for_each, but the auths input is converted to a map which will ensure a "key" is present when looping through instead of "index"

Steps to Reproduce

1. Add a bunch of auths and apply code
2. Add some new ones, and apply code
3. If index ordering changes this will create/delete auth blocks (meaning the db will lose connectivity during the change)

Screenshots

not available at this time, just previous experience with this particular resource

Environment (please complete the following information):

Anything that will help us triage the bug will help. Here are some ideas:
terraform 1.3.6
aws provider 4.51.0

Additional Context

n/a