Merge 80c3574f6c into 1b4497fc8f

By default when there is no region set:
```
$ asp <my-profile>
$ env | grep -i aws
AWS_DEFAULT_PROFILE=<my-profile>
AWS_PROFILE=<my-profile>
AWS_EB_PROFILE=<my-profile>
AWS_REGION=
AWS_DEFAULT_REGION=
```

we get this error for this command if we are using regional STS endpoints:
```
$ aws sts get-caller-identity | jq .Arn

Invalid endpoint: https://sts..amazonaws.com
```

This PR ensures that a default region is always set. By default comes from `default` profile configuration, and defaults to `us-east-1`

plugins/aws/README.md

@@ -96,3 +96,14 @@ source_profile = source-profile-name
 region = us-east-1
 output = json
 ```
+
+## NOTES
+1. If we see an issue with a `aws` CLI command for a specific region e.g:
+   ```shell
+   $ aws eks list-clusters --region me-central-1
+   An error occurred (UnrecognizedClientException) when calling the ListClusters operation: The security token included in the request is invalid
+   ```
+   Ensure you're fetching the AWS credentials from a regional STS endpoint i.e:
+   ```shell
+   $ AWS_STS_REGIONAL_ENDPOINTS=regional gimme-aws-creds
+   ```

plugins/aws/aws.plugin.zsh

@@ -43,6 +43,15 @@ function asp() {
   export AWS_EB_PROFILE=$1
 
   export AWS_PROFILE_REGION=$(aws configure get region)
+  if [[ -z "${AWS_PROFILE_REGION}" ]]; then
+    if [[ -z "${available_profiles[(r)default]}" ]]; then
+      echo "region defaulting to us-east-1"
+      export AWS_PROFILE_REGION=us-east-1
+    else
+      export AWS_PROFILE_REGION=$(aws configure get region --profile default)
+    fi
+  fi
+  export AWS_REGION=$AWS_PROFILE_REGION
 
   _aws_update_state