Upgrade boto3(1.28.*) to allow Service-specific endpoints

[hamishhossack]

Is your feature request related to a problem? Please describe.

Using the importorganisationfroms3 feature to replicate an instance across different environments. This will use an aws bucket to import the config json as defined by the documentation. In this instance, we're using localstack to configure a mocked aws client in local and test environments.

Essentially the change would be bump boto3 to 1.28.0 or later, however, this could impact other features using boto3, eg. dynamodb within the edge proxy. If so, please see the alternative methods.

Describe the solution you'd like

The ability to define which aws client we can use would be greatly appreciated, this would want to be with minimal config change and just using environment variables.

Using these Service-Specific endpoints would be great for the s3 importer.

Setting AWS_ENDPOINT_URL on the docker image and boto3 should pick up the localstack instance via the endpoint when this variable is set.

Describe alternatives you've considered

An alternative and simplier approach could be just to define a AWS_S3_ENDPOINT_URL in the flagsmith config, much like the SES variable found here and using this within the importer to set the endpoint_url in the s3_client here.

An alternative could be, allowing custom boto3 configurations, either created in the docker image or just extending flagsmith as a base image.

Additional context

version 1.28.0 CHANGELOG where this feature is introduced: https://github.com/boto/boto3/blob/develop/CHANGELOG.rst#L601
conversation on this feature for boto3: boto/boto3#2099 (comment)

[dabeeeenster]

Nice idea - happy to receive a PR for this if you have time!

[matthewelwell]

Resolved in #2926