Add AwsSystemsManagerParameterStoreSettingsSource

[alukach]

What I'm adding

In a spirit similar to #175, this PR adds support for AWS Systems Manager Parameter Store. The name is a bit of a mouthful, but I errored on the side of verbosity and named the source AwsSystemsManagerParameterStoreSettingsSource. Something like AwsSsmParameterStoreSettingsSource might be better.

For Pydantic v1, we have been using https://github.com/developmentseed/pydantic-ssm-settings/ on a number of projects, however having the functionality included in Pydantic Settings core seems preferred.

How I did it

I more or less copied the pattern of AzureKeyVaultSettingsSource.

Uncertainties

The testing mocks out the AWS SSM Client, however typically I use something like moto to mock out the AWS services when testing. I wasn't sure about this project's appetite for the added test dependency.

Additionally, I was a bit uncertain about typing the SSMClient. Projects like boto3-stubs provide such types, however I wasn't sure about the project's appetite for adding this dependency.

[hramezani]

Thanks @alukach for this PR.

First of all, I'm not sure we will support this settings source.
I'll check with the team and get back to you first.

[alukach]

@hramezani Sounds good, I'll stand by and wait for the green light before committing any more time to this. Given @samuelcolvin's endorsement of supporting AWS SecretsManager, I figured AWS Parameter Store wouldn't be much of a stretch. Once this is merged, I intend also to add functionality similar to Secrets Manager.

[hramezani]

@alukach I discussed with the team and we decided to not accept this source for now. because:

• It makes the code base mode complex. we need to maintain and handle one more settings source
• There is a possibility for users to have their own settings source
• It is not much request from users for this settings source.

BTW, if we get requests for this settings source, we can add it later.

Thanks for your effort!

[alukach]

@hramezani thanks for the quick follow up. I'll close this and track the feature request as an issue (#399).