[10.x] Do not add token to AWS credentials without validating it first

[mmehmet]

In the CacheManager and FilesystemManager the config that is used to instantiate a new AWS client checks for key and secret values within provided array, before adding those to the credentials element of the config. Unfortunately it also adds a token value, without a similar validation - which can lead to including a blank token value unnecessarily.

Worse still, including a blank token value within that config's credentials array can cause requests using these clients to fail - producing errors such as this when using a DynamoDbClient (which extends the AwsClient) created by a CacheManager that has included such a blank token value:

UnrecognizedClientException (client): The security token included in the request is invalid. - {
    "__type": "com.amazon.coral.service#UnrecognizedClientException",
    "message": "The security token included in the request is invalid."
} {"exception":"[object] (Aws\\DynamoDb\\Exception\\DynamoDbException(code: 0): Error executing \"PutItem\" on \"https://dynamodb.ap-southeast-2.amazonaws.com\"; AWS HTTP error: Client error: `POST https://dynamodb.ap-southeast-2.amazonaws.com` resulted in a `400 Bad Request` response:
{\"__type\":\"com.amazon.coral.service#UnrecognizedClientException\",\"message\":\"The security token included in the request i (truncated...)
UnrecognizedClientException (client): The security token included in the request is invalid. - {\"__type\":\"com.amazon.coral.service#UnrecognizedClientException\",\"message\":\"The security token included in the request is invalid.\"} at /var/task/vendor/aws/aws-sdk-php/src/WrappedHttpHandler.php:195)
[stacktrace]

Not including a (blank) token value in the config fixes this problem.

[joedixon]

Thanks @mmehmet - we only need to ensure token is removed from the top-level array as per the pull request you linked recently.

If you don't want to send a token with the credentials array, then you can remove it from your config file. It's not something that ships with the default config so is only an issue if you are updating it.