backend/s3: Deprecate AWS_???_ENDPOINT environment variables and replace with TF_S3_???_ENDPOINT

[gdavison]

Use-cases

The S3 backend can use the environment variables AWS_IAM_ENDPOINT, AWS_S3_ENDPOINT, AWS_STS_ENDPOINT, and AWS_DYNAMODB_ENDPOINT to override the corresponding AWS API service endpoints. Environment variables starting with AWS_ should be considered as reserved by AWS themselves, and the S3 backend should avoid conflicting with potential future environment variables defined by AWS.

Proposal

The existing environment variables should be deprecated and the environment variables described at https://docs.aws.amazon.com/sdkref/latest/guide/ss-endpoints-table.html, AWS_ENDPOINT_URL_IAM, AWS_ENDPOINT_URL_S3, AWS_ENDPOINT_URL_STS, and AWS_ENDPOINT_URL_DYNAMODB should be added.

They will eventually be added to the AWS SDK (aws/aws-sdk-go-v2#2226)

[jhoelzel]

What do people do on non aws s3 endpoints? currently everything is broken because it can not find an iam. which i wont need on digitalocean.

│ Error: Retrieving AWS account details: AWS account ID not previously found and failed retrieving via all available methods. See https://www.terraform.io/docs/providers/aws/index.html#skip_requesting_account_id for workaround and implications. Errors: 2 errors occurred:
│ 	* retrieving caller identity from STS: operation error STS: GetCallerIdentity, https response error StatusCode: 403, RequestID: 0da35d8e-5b58-48ca-a43d-1e6e735aedf7, api error InvalidClientTokenId: The security token included in the request is invalid.
│ 	* retrieving account information via iam:ListRoles: operation error IAM: ListRoles, https response error StatusCode: 403, RequestID: e209a1b2-03ce-4ab6-b724-634f3d80aace, api error InvalidClientTokenId: The security token included in the request is invalid.

[vineelachavali]

Was above issue fixed? "What do people do on non aws s3 endpoints? currently everything is broken because it can not find an iam. which i wont need on digitalocean." As its broken for us too on similar senario

[kevinisageek]

@jhoelzel @vineelachavali #33981 (comment) seems to do the job

[github-actions]

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