Bug: Metric.add_dimension doesn't aggregate

[cfchou]

Expected Behaviour

https://awslabs.github.io/aws-lambda-powertools-python/latest/core/metrics/#getting-started

Tip
You can initialize Metrics in any other module too. It'll keep track of your aggregate metrics in memory to optimize costs (one blob instead of multiples).

I may be wrong but I think this behavior should also apply to add_dimension. I expect to be able to add_dimension or add_metrics to any Metrics instance. When serializing any one of the instances, an EMF blob is created and it has all metrics and dimensions.

Current Behaviour

When serializing a Metrics instance, dimensions added to other instances do not appear.

Code snippet

def test_metrics_reuse_dimension_set(metric, dimension, namespace):
    # GIVEN Metrics is initialized
    my_metrics = Metrics(namespace=namespace)
    my_metrics.add_dimension(**dimension)
    my_metrics.add_metric(**metric)

    # WHEN Metrics is initialized one more time
    my_metrics_2 = Metrics(namespace=namespace)

    # THEN Both class instances should have the same dimension set
    assert my_metrics_2.dimension_set == my_metrics.dimension_set

### Possible Solution

_No response_

### Steps to Reproduce

1. Create two `Metrics` instances
2. Pick one to add_metric and add_dimension
3. Serialize another one

### AWS Lambda Powertools for Python version

latest

### AWS Lambda function runtime

3.8

### Packaging format used

PyPi

### Debugging logs

_No response_

[boring-cyborg]

Thanks for opening your first issue here! We'll come back to you as soon as we can.
In the meantime, check out the #python channel on our AWS Lambda Powertools Discord: Invite link

[heitorlessa]

Thank you @cfchou for raising this - this is a bug. Investigating and once we have a fix we'll make a patch release ASAP

[heitorlessa]

Got a fix (thanks to your quick tests too!). Triple checking if I haven't missed anything else before we make a release

[github-actions]

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[heitorlessa]

Making a patch release and will share more info soon.

[github-actions]

This is now released under 1.31.0 version!

[heitorlessa]

Publishing Lambda Layer across 22 AWS regions, should be live in ~10m. Will post here when done.

[heitorlessa]

Lambda Layer deployment complete - new version is 38 across all regions.

e.g., arn:aws:lambda:eu-west-1:017000801446:layer:AWSLambdaPowertoolsPython:38.

Please let us know if this somehow doesn't solve your end @cfchou. Thank you one more time for this great bug report!